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CHAPTER IV

Selection of

Glazing Materials

August 2012

ASSOCIATION OF ARCHITECTURAL ALUMINIUM MANUFACTURERS OF SOUTH AFRICA

Trading as the AAAMSA Group Registration #: 1974/00006/08

Association Incorporated under Section 21 P O Box 7861 1ST Floor, Block 4 HALFWAY HOUSE Conference Centre 1685 2nd Road

Midrand 1685 (011) 805-5002 Fax: (011) 805-5033 e-mail: [email protected] additional e-mail: [email protected] web-site: www.aaamsa.co.za ACKNOWLEDGEMENTS

Aluminium Verlag – Düsseldorf Fensterbau mit Aluminium – Walter Schmidt

American Architectural Manufacturers Association Metal Curtain Walls/Windows and Sliding Glass Doors/Aluminium Store Front and Entrances/Skylights and Space Enclosures

ASTM International E1300 Koninklijk Technicum PBNA

Staalcontructies 43A.VR South African Bureau of Standards

SANS 10160, SANS 10137, SANS 10400, SANS 204, SANS 613 and SANS 549 Southern African Institute of Steel Construction

Southern African Steel Construction Handbook Verlag Stahleisen M.B.H. Düsseldorf

Stahl im Hochbau Building Code Australia

BCA 2007 Volume 1 & 2 W.W. Norton & Company

Window Systems for High Performance Buildings Lawrence Berkeley National Laboratory

Therm/Windows/Resfen/Optics National Fenestration Rating Council

Procedure Manuals Note: This Selection Guide replaces the following AAAMSA Publication which is hereby withdrawn in its entirety:

Selection Guide for Glazed Architectural Aluminium Products – Introducing Energy Efficiency in Fenestration – June 2008

Any information contained in Selection Guides of earlier dates, which contradicts with data contained in this manual, is information superseded by this publication

AAAMSA – April 2012

DISCLAIMER All information, recommendation or advice contained in this AAAMSA Publication is given in good faith to the best of AAAMSA’s knowledge and based on current procedures in effect. Because actual use of AAAMSA Publications by the user is beyond the control of AAAMSA such use is within the exclusive responsibility of the user. AAAMSA cannot be held responsible for any loss incurred through incorrect or faulty use of its Publications. Great care has been taken to ensure that the information provided is correct. No responsibility will be accepted by AAAMSA for any errors and/or omissions, which may have inadvertently occurred. This Guide may be reproduced in whole or in part in any form or by any means provided the reproduction or transmission acknowledges the origin and copyright date.

Copyright AAAMSA 2012

4. SELECTION OF TYPES OF GLAZING MATERIALS 4.1 INTRODUCTION

Glass and plastic glazing are usually selected on merits of economics, aesthetics and performance but all glazing is to be executed in strict accordance of the latest editions of the following South African Standards:

National Building Regulations Part N - Glazing SANS 10137 - Code of Practice for the Installation of Glazing Materials in Buildings SANS 10400: Part N - The Application of the National Building Regulations – Glazing SANS 10400:Part XA – The Application of the National Building Regulations – Energy Efficiency in Buildings SANS 1263 - Safety and security glazing materials for buildings Part I Safety performance of glazing materials under human impact Part II Burglar-resistance and vandal resistant glazing materials Part III Bullet-resistant glazing materials SANS 204: Energy Efficiency in Buildings

Float, toughened, laminated, wired and patterned glass is currently used in the building industry. Laminated safety glass is currently locally produced using the following manufacturing process.

Laminated safety glass using poly-vinyl butyral (PVB) interlayer is supplied in three strengths namely Normal Strength (N.S.), High Penetration Resistance (H.P.R.) and High Impact (H.I.).

Specifiers and manufacturers must ensure that the manufacturer of any laminated glass provides a warranty of not less than 5 (five) years against delamination and colour degradation, confirming that the product confirms to that section of SANS 1263 which pertains to the particular application of safety glass i.e., for resistance to human impact (Part I) or to burglary and vandalism (Part II), or to firearms (Part III).

Note! In terms of SANS 1263-Part 1 glass with applied film (organic coating) is not regarded as a safety glazing

material unless it meets all requirements of SANS 1263-Part I (including the boil and artificial ageing tests). In addition the applied film must cover the entire surface of the glazing material i.e. the film must be retained in the glazing rebate.

General applications of glass types Condition Glass and Plastics Human safety (SANS 1263 - Part 1) Laminated glass or toughened glass or polycarbonate Security (smash and grabs, riots, bombs, fire arms, petrol bombs etc.)

Laminated or multi-laminated or Bullet Resisting Glass or polycarbonate (SANS 1263 Parts II and III)

Heavy human traffic (i.e. Balustrades) Toughened Glass or polycarbonate (SANS 1263 Part I)

Fire Wired glass or laminated wired glass or laminated glass with intumescent interlayers or Borosilicate and calcium silicate glass

Unframed applications (suspended assemblies, unframed doors, etc) Toughened Glass or polycarbonate (SANS 10137)

Overhead glazing

Laminated or Wired glass (wired in the case where penetration of glass or water ingress is not a problem) or toughened glass (only permitted when supported all round (SANS 10137) or acrylic or polycarbonate

Sound Control Laminated glass or Sealed Insulated glass units or acrylic or polycarbonate

Solar Control Tinted, reflective and or low-e glass or Sealed Insulated glass units incorporating these or acrylic or polycarbonate

Condensation Sealed insulated glass units or acrylic or polycarbonate One-way vision Reflective glass or acrylic or polycarbonate Ultra-Violet Elimination Laminated glass or acrylic or polycarbonate Fish tanks Domestic Annealed float glass (SANS 17) or acrylic or polycarbonate Underwater Observation panels Multi-laminated glass or acrylic or polycarbonate Floor & Stair treads Multi-laminated glass or acrylic or polycarbonate

4.2 PERFORMANCE OF GLASS PRODUCTS An important aspect of glass selection is the performance of glass in respect of its sound insulation, heat loss and heat gain properties. Although the discussion of the merits of these properties falls outside the scope of the Selection Guide some guidance is provided to the specifier in the following paragraphs.

Due to the vast variety of glass and plastic types the specifier is urged to consult the manufacturer or competent person (glazing) to obtain the relevant technical glass and plastics specifications.

4.3 SOUND INSULATION NOTE: i) Thickness for thickness, clear float, toughened, wired, coated and tinted monolithic glass products have

exactly the same acoustic performance. ii) Data provided is intended as a guide only. Due to the numerous possible computations, data is to be

confirmed with the glass and plastics manufacturer or competent person (glazing). 1. SINGLE GLAZING

Monolithic Glass Glass thickness 4 6 10 12 Rw Index (ISO 717) 27 29 33 34

Laminated Glass Glass thickness 6.38 8.38 17 Rw Index (ISO 717) 32 34 41

2. SEALED INSULATED GLASS UNITS (Double glazing)

Monolithic glass and monolithic glass Glass/Space/Glass thickness 4/12/4 6/12/6 Rw Index (ISO 717) 29 30

Laminated glass and monolithic glass Glass/Space/Glass thickness 6.38/12/6 Rw Index (ISO 717) 36

3. DOUBLE WINDOWS (Secondary sash)

Glass/Space/Glass thickness 6/150/4 10/200/6 Rw Index (ISO 717) 45 47

4.4 ENERGY RELATED PROPERTIES OF WINDOWS 4.4.1 PROPERTIES OF GLAZING THAT AFFECT ENERGY PERFORMANCE

` Figure 4.1: Solar radiation through a glazing material is reflected, transmitted or absorbed

Most window and façade assemblies consist of glazing and frame components. Glazing may be a single pane of glass (or plastic) or multiple panes with air spaces in between. These multiple layer units, referred to as insulating glazing units (IGU), include spacers around the edge and sometimes low-conductance gases in the spaces between glass panes. Coatings and tins affect the performance of the glazing. The IGU is placed within a frame of aluminium, steel, wood, plastic, or some hybrid or composite material. Some curtain wall systems using structural sealants and other special fittings have no exterior frame. Heat flows through a window assembly in three ways: conduction, convection, and radiation. Conduction is heat travelling through a solid, liquid or gas. Convection is the transfer of heat by the movement of gases or liquids, like warm air rising from a candle flame. Radiation is the movement of energy through space without relying on conduction through the air or by movement of the air, the way you feel the heat of a fire. When there is a temperature difference across an object (i.e., when a window separates a cold outdoors from a warm interior or a hot outside from a conditioned interior space), heat transfer will occur via these three physical mechanisms: conduction through glass and solid frame materials, convection/conduction through air spaces, and long-wave radiation between glass surfaces on either side of an air gap. This temperature-driven heat transfer is quantified by the term U-factor and is discussed in the section on insulating value. There are two distinct types of radiation or radiation heat transfer:

Long-wave radiation heat transfer refers to radiant heat transfer between objects at room or outdoor environmental temperatures. These temperatures emit radiation in the rage of 3-50 microns.

Short-wave radiation heat transfer refers to radiation from the sun (which is at a temperature of 6000K) and occurs in the 0.3-2.5 micron range. This range includes the ultraviolet, visible, and solar-infrared radiation (Figure 4.2)

1. Idealized transmittance of a glazing with a low-E coating designed for low solar heat gain. Visible light is transmitted and solar-infrared radiation is reflected. Long-wave infrared radiation is reflected back into the interior. This approach is suitable for commercial buildings in almost all climates.

2. Idealized transmittance of a glazing with a low-E coating designed for high solar heat gain. Visible light and solar-infrared radiation are transmitted. Long-wave infrared radiation is reflected back into the interior. This approach is more commonly used for residential windows in cold climates.

Note: As shown by the solar spectrum in the figure, sunlight is composed of electromagnetic radiation of many wavelengths, ranging from short-wave invisible ultraviolet to the visible spectrum to the longer, invisible solar-infrared waves.

Figure 4.2: Ideal spectral transmittance for glazing in different climates

Even though the physical process is the same, there is no overlap between these two wavelength ranges. Coatings that control the passage of long wave or solar radiation in these ranges, through transmission and/or reflection, can contribute significantly to energy savings and have been the subject of significant innovations in recent years. Glazing types vary in their transparency to different parts of the visible spectrum. For example, a glass that appears tinted green as you look through it toward the outdoors transmits more sunlight from the green portion of the visible spectrum and absorbs or reflects more of the other colours. Similarly, a bronze-tinted glass absorbs or reflects the blues and greens and transmits the warmer colours. Neutral gray tints absorb or reflect most colours equally. The same principle applies outside the visible spectrum. Most glass is particularly transparent to at least some ultraviolet radiation, while plastics are commonly more opaque to ultraviolet. Glass is opaque to long-wave infrared radiation but generally transparent to solar-infrared radiation. Strategic utilization of these variations has made some high-performance glazing products. The four basic properties of glazing that affect radiant energy transfer-transmittance, reflectance, absorptance, and emittance – are described below.

4.4.2 TRANSMITTANCE Transmittance refers to the percentage of radiation that can pass through glazing. Transmittance can be defined for different types of light or energy, e.g., visible transmittance, UV transmittance, or total solar energy transmittance. Transmission of visible light determines the effectiveness of a type of glass in providing daylight and a clear view through the window. For example, tinted glass has a lower visible transmittance than clear glass. While the human eye is sensitive to light at wavelengths from about 0.4 to 0.7 microns, its peak sensitivity is at 0.55, with lower sensitivity at the red and blue ends of the spectrum. This is referred to as the photonic sensitivity of the eye. More than half of the sun’s energy is invisible to the eye. Most reaches us as near-infrared with a few percent in the ultraviolet (UV) spectrum. Thus, total solar energy transmittance describes how the glazing responds to a much broader part of the spectrum and is more useful in characterizing the quantity of total solar energy transmitted by the glazing. With the recent advances in glazing technology, manufacturers can control how glazing materials behave in these different areas of the spectrum. The basic properties of the substrate material (glass or plastic) can be altered, and coatings can be added to the surfaces of the substrates. For example, a window optimized for day lighting and for reducing overall solar heat gains should transit an adequate amount of light in the visible portion of the spectrum, while excluding unnecessary heat gain from the near-infrared part of the electromagnetic spectrum. 4.4.3 REFLECTANCE Just as some light reflects off of the surface of water, some light will always be reflected at every glass surface. A specular reflection from a smooth glass surface is a mirror like reflection similar to the image of yourself you see reflected in a store window. The natural reflectivity of glass is dependent on the type of glazing material, the quality of the glass surface, the presence of coatings, and the angle of incidence of the light. Today, virtually all glass manufactured in the United States is float glass, which reflects 4 percent of visible light at each glass-air interface or 8 percent total for a single pane of clear, uncoated glass. The sharper the angle at which the light strikes, however, the more the light is reflected rather than transmitted or absorbed (Figure 4.3). Even clear glass reflects 50% or more of the sunlight striking it at incident angles greater than about 80°. (The incident angle is formed with respect to a line perpendicular to the glass surface).

Figure 4.3: Sunlight transmitted and reflected by 6mm

clear glass as a function of the incident angle

The reflectivity of various glass types becomes especially apparent during low light conditions. The surface on the brighter side acts like a mirror because the amount of light passing through the window from the darker side is less than the amount of light being reflected from the lighter side. This effect can be noticed from the outside during the day and from the inside during the night. For special applications when these surface reflections are undesirable (i.e., viewing merchandise through a store window on a bright day), special coatings can virtually eliminate this reflective effect. Most common coatings reflect in all regions of the spectrum. However, in the past 20-years, researches have learned a great deal about the design of coatings that can be applied to glass and plastic to preferentially reflect only selected wavelengths of radiant energy. Varying the reflectance of far-infrared and near-infrared energy has formed the basis for high-performance low-E coatings. 4.4.4 ABSORPTANCE Energy that is not transmitted through the glass or reflected off its surfaces is absorbed. Once glass has absorbed any radiant energy, the energy is transformed into heat, raising the glass temperature. Typical 6mm clear glass absorbs only about 7% of sunlight at a normal angle of incidence (also a 30° angle of incidence, as shown in Figure 4.3). The absorptance of glass is increased by glass additives that absorb solar energy. If they absorb visible light, the glass appears dark. If they absorb ultraviolet radiation or near-infrared, there will be little or no change in visual appearance. Clear glass absorbs very little visible light, while dark-tinted glass absorbs a considerable amount (Figure 4.4).

Figure 4.4: Solar energy transmission through three types of glass under standard ASHRAE summer conditions

The absorbed energy is converted into heat, warming the glass, thus, when “heat-absorbing” glass is in the sun, it feels much hotter to the touch than clear glass. Tints are generally gray, bronze, or blue-green and were traditionally used to lower the solar heat gain coefficient and to control glare. Since they block some of the sun’s energy, they reduce the cooling load placed on the building and its air-conditioning equipment. The effectiveness of heat-absorbing single glazing is significantly reduced if cool, conditioned air flows across the glass. Absorption is not the most efficient way to reduce cooling loads, as discussed later. All glass and most plastics, however, are generally very absorptive of long-wave infrared energy. This property is best illustrated in the use of clear glass for greenhouses, where it allows the transmission of intense solar energy but blocks the retransmission of the low-temperature heat energy generated inside the greenhouse and radiated back to the glass. 4.4.5 EMMITTANCE When solar energy is absorbed by glass, it is either converted away by moving air or reradiated by the glass surface. This ability of a material to radiate energy is called its emissivity. Window glass, along with all other objects, typically emits, or radiates, heat in the form of long-wave far-infrared energy. The wavelength of the long-wave far-infrared energy varies with the temperature of the surface. This emission of radiant heat is one of the important heat transfer pathways for a window. Thus, reducing the window’s emission of heat can greatly improve its insulating properties. Standard clear glass has an emittance of 0.84 over the long-wave infrared portion of the spectrum, meaning that it emits 84% of the energy possible for an object at room temperature. It also means that for long-wave radiation striking the surface of the glass, 84% is absorbed and only 16% is reflected. By comparison, low-E glass coatings have an emittance as low as 0.04. This glazing would emit only 4% of the energy possible at its temperature and thus reflect 96% of the incident long-wave infrared radiation.

4.5 DETERMINING ENERGY-RELATED PROPERTIES OF WINDOWS There are four properties of windows that are the basis for quantifying energy performance:

U-factor. When there is a temperature difference between inside and outside, heat is lost or gained through the window frame and glazing by the combined effects of conduction, convection, and long-wave radiation. The U-factor of a window assembly represents its overall heat transfer rate or insulating value.

Solar Heat Gain Coefficient. Regardless of outside temperature, heat can be gained through windows by direct

or indirect solar radiation. The ability to control this heat gain through windows is characterized in terms of the solar heat gin coefficient (SHGC) or shading coefficient (SC) of the window.

Visible Transmittance. Visible transmittance (VT), also referred to as visible light transmittance (VLT), is an

optical property that indicates the amount of visible light transmitted through the glass. It affects energy by providing daylight that creates the opportunity to reduce electric lighting and its associated cooling loads.

Air Leakage. Heat loss and gain also occur by air leakage through cracks around sashes and frames of the

window assembly. This effect is often quantified in terms of the amount of air (cubic meters per minute) passing through a unit area of window (square metre) under given pressure conditions.

These four concepts – as well as Light-to-Solar-Gain ratio, a ratio of VT/SHGC – have been standardized within the glazing industry, and allow accurate comparison of windows.

4.5.1 INSULATING VALUE (U-factor) For windows, a principle energy concern is their ability to control heat loss. Heat flows from warmer to cooler bodies, thus from the inside face of a window to the outside in winter, reversing direction in summer. Overall heat flow from the warmer to cooler side of a window unit is a complex interaction of all three basic heat transfer mechanisms – conduction, convection, and long-wave radiation (Figure 4.5). A window assembly’s capacity to resist this heat transfer is referred to as its insulating value. Conduction occurs directly through glass, and the air cavity within double-glazed SIGUs, as well as through a window’s spacers and frames. Some frame materials, like wood, have relatively low conduction rates. The higher conduction rates of other materials, like metals, have to be mitigated with discontinuities of thermal breaks in the frame to avoid energy loss.

Figure 4.5: Components of heat transfer

through a window that are related to U-factor

Convection within a window unit occurs in three places: the interior and exterior glazing surfaces, and within the air cavity between glazing layers. On the interior, a cold interior glazing surface chills the adjacent air. This denser cold air then falls, starting convection current. People often perceive this air flow as a draft caused by leaky windows, instead of recognizing that the remedy correctly lies with a window that provides a warmer glass surface (Figure 2-6). On the exterior the air film against the glazing contributes to the window’s insulating value. As wind blows (convection), the effectiveness of this air film is diminished, contributing to a higher heat rate loss. Within the air cavity, temperature-induced convection currents facilitate heat transfer. By adjusting the cavity width, adding more cavities, or choosing a gas fill that insulates better than air, windows, can be design to reduce this effect. All objects emit invisible thermal radiation, with warmer objects emitting more than colder ones. Through radiant exchange, the objects in the room, and especially the people (who are often the warmest objects), radiate their heat to the colder window. People often feel the chill from this radiant heat loss, especially on the exposed skin of their hands and faces, but they attribute the chill to cool room air rather than to a cold window surface. Similarly, if the glass temperature is higher than skin temperature, which occurs when the sun shines on heat-absorbing glass, heat will be radiated from the glass to the body, potentially producing thermal discomfort. The complex interaction between conduction, convection, and radiation is perhaps best illustrated by the fact that the thermal performance of a roof window or skylight changes according to its mounting angle. Convective exchange on the inner and outer glazing surfaces, as well as that within the air cavity is affected by this slope. Also, skylights and roof windows oriented toward the cold night sky lose more radiant heat at night than windows viewing warmer objects, such as the ground, adjacent buildings, and vegetation. 4.5.1.1 DETERMINING INSULATING VALUE The U-factor (also referred to as U-value) is the standard way to quantify overall heat flow. For windows, it expresses the total heat transfer coefficient of the system, and includes conductivity, convective, and radiative heat transfer. It represents the heat flow per hour (in watts) through each square metre of window for a 1° Kelvin temperature difference between the indoor and outdoor air temperature. The insulating value of R-value (resistance to heat transfer) is the reciprocal of the total U-factor (R=1/U). The higher the R-value of a material, the higher the insulating value; the smaller the U-factor, the lower the rate of heat flow. Given that the thermal properties and the various materials within a window unit, the U-factor is commonly expressed in two ways:

The U-factor of the total window assembly combines the insulating value of the glazing proper, the edge effects in the SIGU, and the window frame and sash.

The centre-of-glass U-factor assumes that heat flows perpendicular to the window plane, without addressing the impact of the frame edge effects and material.

The U-factor of the glazing portion of the window unit is affected primarily by the total number of glazing layers, their dimension, the type of gas within their cavity, and the characteristic of coatings on the various glazing surfaces. As windows are complex three-dimensional assemblies, in which materials and cross sections change in a relatively short distance, it is limiting, however, to simply consider glazing. For example, metal spacers at the edge of an IGU have a much higher heat flow than the centre of the insulation glass, which causes increased heat loss along the outer edge of the glass.

4.5.1.2 OVERALL U-FACTOR The relative impact of these “edge effects” becomes more important as the insulating value of the entire assembly increases, and in small units were the ratio of edge to centre-of-glass area is high. Since the U-factors vary for the glass, edge-of-glass zone, and frame, it can be misleading to compare the U-factors of windows from different manufacturers if they are not carefully and consistently described. Calculation methods developed by the National Fenestration Rating Council (NFRC) address this concern. A specific set of assumptions and procedures must be followed to calculate the overall U-factor of a window unit using the NFRC method. For instance, the NFRC values are for a standard window size – the actual U-factor of a specific unit varies with size. The U-factor of a window unit is rated based on a vertical position. A change in mounting angle affects a window’s U-factor. The same unit installed on a sloped roof at 20° from horizontal would have a U-factor 10-20% higher than in the vertical position (under winter conditions). 4.5.2 SOLAR RADIATION CONTROL The second major energy-performance characteristic of windows is the ability to control solar heat gain through the glazing. Solar heat gain through windows is a significant factor in determining the cooling load of many commercial buildings. The origin of solar heat gain is the direct and diffuse radiation coming from the sun and the sky (or reflected from the ground and other surfaces). Some radiation is directly transmitted through the glazing to the building interior, and some may be absorbed in the glazing and indirectly admitted to the inside. Some radiation absorbed by the frame will also contribute to overall window solar heat gain factor. Other thermal (non-solar) heat transfer effects are included in the U-factor of the window). 4.5.2.1 DETERMINING SOLAR HEAT GAIN There are two metrics for quantifying the solar radiation passing through a window: solar heat gain coefficient (SHGC) and shading coefficient (SC). In both cases, the solar heat gain is the combination of directly transmitted radiation and the inward-flowing portion of absorbed radiation (Figure 4.6). However, SHGC and SC have a difference basis for comparison. 4.5.2.2 SHADING COEFFICIENT Until the mid-1990s, the shading coefficient (SC) was the primary term used to characterize the solar control properties of glass. Although replaced by NFRC and ASHRAE with the solar heat gain coefficient (SHGC), it is still referenced in books and product literature, and is expressed as a dimensionless number from 0-1 – high shading coefficient means high solar gain, while a low shading coefficient means low solar gain. The SC was originally developed as a single number that could be used to compare glazing solar control under a wide range of conditions. Its simplicity, however, is offset by its inaccuracies.

Figure 4.6. Simplified view of the

components of solar heat gain. Heat gain includes the transmitted solar energy and

the inward flowing components ob absorbed radiation

For instance, the shading coefficient (SC) is only defined for the glazing portion of the window and does not include frame effects. It represents the ratio of solar heat gain through the system relative to that through 6mm clear glass at normal incidence. The SC has also been used to characterize performance over a wide range of sun positions; however, there is some potential loss in accuracy when applied to sun positions at high angles to the glass. The SC value is strongly influenced by the type of glass selected. The shading coefficient can also include the effects of any integral part of the window system that reduces the flow of solar heat, such as multiple glazing layers, reflective coatings, or blinds between layers of glass.

4.5.2.3 SOLAR HEAT GAIN COEFFICIENT Window standards are now moving away from shading coefficient to solar heat gain coefficient (SHGC), which is defined as that fraction of incident solar radiation that actually enters a building through the window assembly as heat gain. The SHGC is influenced by all the same factors as the SC, but since it can be applied to the entire window assembly, the SHGC is also affected by shading from the frame as well as the ratio of glazing and frame. The solar heat gain coefficient is expressed as a dimensionless number from 0-1. A high coefficient signifies high heat gain, while a low coefficient means low heat gain. For any glazing, the SHGC is always lower than the SC. To perform an approximate conversion from SC to SHGC, multiply the SC value by 0.87. Since the frame area has a very low SHGC, the overall window SHGC is lower than the centre-of-glass value. 4.5.3 VISIBLE TRANSMITTANCE Visible transmittance (VT), also referred to as visible light transmittance (VLT), is the amount of light in the visible portion of the spectrum that passes through a glazing material. A higher VT means there is more daylight in a space which, if designed properly, can offset electric lighting and its associated cooling loads. Visible transmittance of glazing ranges from above 90% for uncoated water-white clear glass to less than 10% for highly reflective coatings on tinted glass. Visible transmittance is influenced by the glazing type, the number of panes, and any glass coatings. VT values for the whole window are always less than centre-of-glass values since the VT of the frame is zero. 4.5.3.1 LIGHT-TO-SOLAR-GAIN RATIO In the past, windows that reduced solar gain (with tints and coatings) also reduced visible transmittance. However, new high-performance tinted glass and low-solar-gain low-E coatings have made it possible to reduce solar heat gain with little reduction in visible transmittance. Because the concept of separating solar gain control and light control is so important, measures have been developed to reflect this. The term luminous efficacy (ke), which is VT/SC, was first developed. Since SC is being replaced by SHGC, the term light-to-solar-gain ratio (LSG) is now referred to in ASHRAE publications. The LSG ratio is defined as a ratio between visible transmittance (VT) and solar heat gain coefficient (SHGC). 4.5.4 OTHER DESIGN/SELECTION CONSIDERATIONS During the glass selection process one requires to consider the needs of the occupants, the Mechanical Engineer and the building design intent. A 60% - 70% Visible Light Transmission is too high for most commercial applications and blinds or window films are necessary for occupant comfort. The use of these interventions e.g. blinds may render the aesthetic appearance of the building to become unacceptable and comparable to “Laundry on the Balcony”. The recommendable Visible Light Transmission creates a more uniform appearance to the building and creates a better colour match between the spandrel and vision glass. Day lighting is another important consideration. Too much light causes glare and the “cave effect” whereby the back of the room appears dark compared to other areas. As a result occupants will close blinds and turn on overhead lights. Well-designed day lighting lets in natural light that balances overhead electric lighting white curtailing glare. Each application needs to be considered on its own merits and the correct glass selection in North America will not necessarily mean that the same glass selection is correct for South Africa. 4.5.5 AIR LEAKAGE (INFILTRATION) Whenever there is a pressure difference between the inside and outside (driven by wind or temperature difference), air will flow through cracks between window assembly components. The air leakage properties of window systems contribute to the overall building air infiltration. Infiltration leads to increased heating or cooling loads when the outdoor air entering the building needs to be heated or cooled. Air leakage also contributes to summer cooling loads by raising the interior humidity level. Operable windows can be responsible for air leakage between sash and frame elements as well as at the window/wall joint. Tight sealing and weather-stripping of windows, sashes, and frames is of paramount importance in controlling air leakage.

The use of fixed windows helps to reduce air leakage because these windows are easier to seal and keep tight. Operable windows, which are also more susceptible to air leakage, are not necessary for ventilation in most commercial buildings but are desired by occupants for control. Operable window units with low air-leakage rates feature mechanical closures that positively clamp the window shut against the wind. For this reason, compression-seal windows such as top hung and side hung designs are generally more effectively weather-stripped than are sliding-seal windows. Sliding windows rely on wiper-type weather-stripping, which is more subject to wear over time. The level of infiltration depends upon local climate conditions, particularly wind conditions and microclimates surrounding the building. In reality, infiltration varies widely with wind-driven and temperature-driven pressure changes. Cracks and air spaces left in the window assembly can also account for considerable infiltration. Insulating and sealing these areas during construction can be very important in controlling air leakage. A proper installation ensures that the main air barrier of the wall construction is effectively sealed to the window or skylight assembly so that continuity of the air barrier is maintained. Air leakage is determined through the test method contained in SANS 613 – Fenestration Products – Mechanical Performance Criteria. This standard is referred to in both SANS 10400:XA - Energy Efficiency in Buildings and SANS 204 – Energy Efficiency in Buildings. In terms of SANS 10400:A General principles and requirements Performance Test Certificates are to be provided by the manufacturer/installers of fenestration products confirming compliance with the air breakage requirements. The Thermal Test Laboratory (TTL) a SANAS accredited test laboratory type tested top hung windows of identical configuration but made from different framing material. The windows were bought “off-the-shelf” from distributors and were found to have different air leakage results when tested in accordance with SANS 613.

PTT Windows 1200w x 1500h – 4mm clear float glass

PTT Windows Thermal Transmittance (W/m2C)

Air leakage Max 2.0ℓ/sec/m2

75Pa Note! Using 4mm clear glass in all instances observe the framing effect on the thermal transmittance and the centre of glass thermal transmittance versus total system U-value.

Steel 5.32 More than 5.787 PVCu 4.36 2.544

Timber 3.92 3.466 Aluminium 5.22 0.376

The impact air infiltration has on the thermal performance of windows is illustrated by the following graphs prepared by Dr. G Genis of the Thermal Testing Laboratory.

4.6 EXPOSURE TO FIRE AND PERFORMANCE OF GLAZING

Window manufacturers/sub contractors and glaziers are no fire experts and it is therefore the onus of the client/specifiers to indicate the glass requirements in respect of location and degree of resistance to fire in minutes. The Architect/ Engineer must specify the glazing requirements in respect of SANS 10400-T. In terms of SANS 10400-T a Competent Person (Fire Engineering) shall specify the fire requirements of glazing in respect of resistance to fire. Aluminium framing will not resist fire when tested in accordance with SANS 10177-2 in excess of 30-minutes. In addition all glazing in atrium buildings and shopping centres are not covered by SANS 10400-T in respect of fire performance and require sign off by Competent Person (Fire Engineering) Framing required for fire resistance in excess of 30-minutes must be manufactured in steel or hard wood of appropriate volume. When tested in accordance with SANS 10177-2 glazing materials may perform as stated in the following Tables.

Fire Resistance Performance of Glass

Glass Type Fire Resistance in minutes Laminated safety glass having PVB/resin interlayer 3 to 6 Laminate glass having intumescent interlayer Up to 120 Georgian wired glass Up to 60 Borosilicate and calcium silicate glass Up to 120 Toughened safety glass 3 to 6 SIGU (double glazing) having PVB/resin laminated safety glass 30

Solid Polycarbonate Sheet Fire Classification*

Country Norm Classification

United Kingdom BS476 Part 7 Building Regulations (1991) 17 27

*Dependant on thickness and colour. Consult manufacturer/suppliers for detailed information. Glass and Polycarbonate flat sheet in and on itself is not fire resistive unless installed in a proper frame. All elements i.e. glass + framing + sealants/gaskets + anchorage + installation quality equal fire resistance performance. The Architectural Aluminium manufacturer/contractor and glazier are not fire consultants and the client/specifier must specify the fire requirement at time of tender taking full cognance of SANS 10400-T. When tested in accordance with SANS 10177-2 the manufacturers may classify their various products as follows:

Example: E130 = 30 minutes integrity with 30 minutes insulation.

E = INTEGRITY Provides a physical barrier against flame, hot toxic gases and smoke. “The ability of the element of construction with a separating function to withstand fire exposure on one side only, without the transmission of fire to the non-fire side as a result of the passage of significant quantities of flames or hot gases from the fire side to the non-fire side, thereby causing ignition of the non-fire exposed surface or any materials adjacent to that surface” W = RADIATION Creating safer escape routes for people and separation distances for combustible materials by controlling the transmission of radiant heat below a specified level, e.g. 15 kW/m2. “The ability of the element of construction with a separating function to withstand fire exposure from one side only for a period of time, while the measured radiated heat in front of the glazing is below a specified level.” I = INSULATION Highest performance limitation of surface temperature on the unexposed side “The ability of the element of construction with a separating function to withstand fire exposure from one side only, without the transmission of fire to the non-fire side as a result of significant conduction of heat from the fire side to the non-fire side, thereby causing ignition of the non-fire exposed surface of any material in contact with that surface and the ability to provide a barrier to heat sufficient to protect people near the element of construction for the relevant classification period.

4.7 LEXAN THERMOCLEAR 4.7.1 LEXAN POLYCARBONATE RESIN Lexan polycarbonate is a unique engineering thermoplastic which combines a high level of mechanical, optical and thermal properties. The versatility of this material makes it suitable for many engineering applications. When extruded in sheet form, it’s optical and impact properties in particular render this material an ideal candidate for a wide range of glazing applications. SABIC Innovative Plastics has developed a whole range of products to suit the most demanding of these application needs. Typical applications include:

Industrial Roofs and Sidewalls Commercial Greenhouses Sunroom, Swimming Pool and Conservatory Roofing Shopping Center Roofing Railway/Metro Station Football Stadium Roofing Roof lights

4.7.2 LEXAN MULTI-WALL SHEET Lexan Thermoclear Plus sheet (LT2UV) Lexan Thermoclear Plus sheet features as of 4.5mm thickness a unique 2 side proprietary surface treatment designed to protect the sheet against the degrading effects of ultra-violet radiation in natural sunlight. 2 sides UV protected surfaces offers advantage in economical cutting the sheet in desired shapes and installation mistakes are minimized since both sheet surfaces may be faced outwards. Lexan Thermoclear SunXP sheet (LT2XP) Lexan Thermoclear SunXP sheet offers next to remarkable impact strength, high light transmission, light weight, long term weather resistance and, due to the multi-wall construction, outstanding thermal insulation properties an even more unique 2 side proprietary surface treatment which provides almost total resistance against degradation caused by UV radiation in sunlight. The entire Lexan Thermoclear SunXP sheet range carries a Fifteen Year Limited Written Warranty against discoloration, loss of light transmission and /or loss of strength due to weathering. Lexan Thermoclear Easyclean sheet (LTE) Lexan Thermoclear Easyclean sheet makes use of a new and innovative technology platform of self-cleaning properties the extraordinary hydrophobic coating on the outside surface reduces the surface tension of polycarbonate and increases the contact angle of water to the sheet this cases larger droplets to form and wash away dirt as the droplets roll down the sheet. Lexan Thermoclear Easyclean comes standard with a unique 2 side UV proprietary surface treatment but can be combined with Dripgard property on the inner side of the sheet forming a unique combination of having a Thermoclear sheet with self-cleaning properties on the outside and a surface treatment on the inside which reduces the formation of condensation droplets to prevent loss of light transmission. Lexan Thermoclear Dripgard sheet (LTD) Lexan Thermoclear Dripgard sheet, in addition to the extraordinary properties of standard 2 side UV resistant Lexan Thermoclear sheet, also features a specially developed coating on the inner surface which reduces the formation of condensation droplets. This property is particularly important in helping to prevent crop spoilage in commercial greenhouses, by falling condensation droplets. There is no reduction in light transmission due to condensation water droplets. It is the ideal roof glazing material in any application where water drops are unacceptable. For instance: greenhouses/verandas/sunrooms/swimming pool enclosures/industrial roof glazing. Lexan Thermoclear Solar Control IR sheet (2UVIR) Lexan Thermoclear Solar Control IR sheet makes use of a new and innovative technology platform of solar energy absorption. The Lexan Thermoclear Solar Control IR sheets are transparent with a green (GN), blue (BL) or grey (GY) tint, which blocks near-Infrared light but let’s in high levels of visible light. Lexan Solar Control IR multiwall sheet offers: high light transmission combined with low solar transmission, 2 sides unique UV protection, various structures (2/3/5/6/9 walls, X structures), long-term weathering resistance and high impact strength. Lexan Thermoclear impact resistant

250 times the impact strength of glass 30 times the impact of acrylic 40% better thermal efficiency than glass Considerably lower maintenance costs than glass or acrylic Wide selection of grades and gauges

General information Lexan Multi-wall Sheet Lexan Thermoclear is an impact resistant, energy saving, multi-wall polycarbonate glazing sheet. It features a proprietary surface treatment which provides almost total resistance against degradation caused by UV radiation in sunlight. The entire Lexan Thermoclear sheet range carries a Ten Year Limited Warranty against:

Discoloration Loss of light transmission Loss of strength due to weathering.

Typical applications include:

Industrial Roofs and Sidewalls Commercial Greenhouses Sunroom, Swimming Pool and Conservatory Roofing Shopping Center Roofing Railway/Metro Station Football Stadium Roofing

Note: This section refers to polycarbonate products. “Lexan” is a registered trade name. No exclusivity has been intended. We acknowledge SABIC Innovative Plastics BV for providing technical information in respect of glazing materials.

Table 4.1 – Typical properties of multi-wall products

Sheet thickness mm Structure

Approx Weight gsm

6 2RS 1300

8 2RS 1500

10 2RS 1700

10 3TS 2000

10 3X

2000

10 5RS 1750

16 3TS 2700

16 3X

2900

16 6RS 2900

20 5RS 3300

25 6RS 3500

32 5X

3800

Clear 112 Light transmission % Total solar transmission % Shading coefficient Solar heat gain coefficient Direct solar transmission % Light to solar gain ratio

82 82

0.94 0.82 76

1.00

81 82

0.94 0.82 77

0.99

81 80

0.92 0.8 76

1.01

74 77

0.89 0.77 70

0.96

71 71

0.82 0.71 67

1.00

65 65

0.75 0.65 61

1.00

74 78

0.90 0.78 70

0.95

67 71

0.82 0.71 63

0.94

61 64

0.74 0.64 57

0.95

64 71

0.82 0.71 60

0.90

58 66

0.76 0.66 54

0.88

55 65

0.75 0.65 54

0.85

Grey 715081 Light transmission % Total solar transmission % Shading coefficient Solar heat gain coefficient Direct solar transmission % Light to solar gain ratio

20 50

0.58 0.5

0.4

20 50

0.58 0.5

0.4

20 50

0.58 0.5

0.4

37 52 0.6

0.52

0.71

Opal WH7A092X Light transmission % Total solar transmission % Shading coefficient Solar heat gain coefficient Direct solar transmission % Light to solar gain ratio

66 69

0.79 0.69 63

0.96

64 68

0.78 0.68 62

0.94

64 68

0.78 0.68 62

0.94

61 66

0.76 0.66 59

0.92

62 67

0.77 0.67 59

0.93

60 59

0.68 0.59 58

1.02

63 69

0.79 0.69 60

0.91

60 64

0.74 0.64 57

0.94

52 60

0.69 0.6 49

0.87

55 60

0.69 0.6 53

0.92

49 63

0.72 0.63 47

0.78

48 48

0.55 0.48 56

1.00

Bronze 515055 Light transmission % Total solar transmission % Shading coefficient Solar heat gain coefficient Direct solar transmission % Light to solar gain ratio

37 58

0.67 0.58 43

0.64

38 59

0.68 0.59 43

0.64

35 55

0.63 0.55 44

0.64

60 59

0.68 0.59 58

1.02

63 69

0.79 0.69 60

0.91

29 53

0.61 0.53 33

0.55

26 50

0.57 0.5

0.52

23 49

0.56 0.49

0.47

Metallic grey GY6A744M Light transmission % Total solar transmission % Shading coefficient Solar heat gain coefficient Direct solar transmission % Light to solar gain ratio

16 34

0.39 0.34 15

0.47

17 31

0.36 0.31 17

0.55

16 29

0.33 0.29 15

0.55

16 30

0.34 0.3 15

0.53

16 22

0.26 0.22 15

0.73

16 28

0.33 0.28 15

0.57

20 32 36

0.32 15

0.63

IR grey GY5B422T Light transmission % Total solar transmission % Shading coefficient Solar heat gain coefficient Direct solar transmission % Light to solar gain ratio

24 46

0.53 0.46 26

0.52

22 42

0.48 0.42 22

0.48

22 30

0.34 0.3 18

0.73

27 40

0.46 0.4 16

0.68

12 30

0.34 0.3 11

0.34

IR green CN8B038T Light transmission % Total solar transmission % Shading coefficient Solar heat gain coefficient Direct solar transmission % Light to solar gain ratio

66 60

0.69 0.6 47 1.1

17 31

0.36 0.31 17

0.55

65 60

0.69 0.6 45

1.08

55 52 0.6

0.52 36

1.06

46 45

0.52 0.45 29

1.02

46 46

0.53 0.46 29 1

41 44 0.5

0.44 26

0.93

36 42

0.49 0.42 23

0.86

IR blue BL8B089T Light transmission % Total solar transmission % Shading coefficient Solar heat gain coefficient Direct solar transmission % Light to solar gain ratio

52 60

0.69 0.6 44

1.08

40 49

0.56

32 0.82

20 36

0.42 0.36 17

0.56

20 35 0.4

0.35 16

0.57

K value Sound insulation db

3.5 18

3.3 18

3 19

2.7 19

2.5 19

2.3 19

2.4 21

2.3 21

1.9 21

1.8 22

1.5 23

1.4 23

Table 4.2: Typical properties for Lexan Polycarbonate Sheet Property Physical Test method Unit Value Density ISO 1183 g/cm3 1,20 Water absorption, 50% RH / 23°C ISO62 % 0,15 Water absorption, saturation / 23°C ISO 62 % 0,35 Mechanical Tensile stress at yield 50mm/min ISO 527 MPa 60 Tensile stress at break 50mm/min ISO 527 MPa 70 Tensile strain at yield 50mm/min ISO 527 % 6 Tensile strain at break 50mm/min ISO 527 % 120 Tensile modulus 2mm/min ISO 527 MPa 2300 Flexural stress at yield 2mm/min ISO 178 MPa 90 Flexural stress at break 2mm/min ISO 178 MPa 2300 Hardness H358/30 95 ISO 2039/1 MPa 95 Thermal Vicat Softening Temperature, rate B/120 ISO 306 °C 145 HTD/Ae, 1.8 MPa edgew. 120*1*04/sp=100 ISO 75 °C 127 Thermal conductivity ISO 8302 W/m.°C 0,2 Coeff. Of lin. Them. Exp.extr.23-80°C ISO 11359-2 1/°C 7.00 E-05 Electrical Volume resistivity IEC 60093 0hm.cm 10E15 These property values have been derived from Lexan resin data for the material used to produce this sheet product. Variations within normal tolerances are possible for various colours. These typical values are not intended for specification purposes. If minimum certifiable properties are required please contact your local SABIC Innovative Plastics, Specialty Film & sheet representative. All values are measured at least after 48 hours storage at 23°C/50% relative humidity. All properties are measured on injection moulded samples. All samples are prepared according ISO 294.

Table 4.3 Typical Properties Thermoclick/Thermopanel

Sheet thickness mm Structure Approx. weight g/m2

40 4X

4000

30 A/4RS 4000

30 B/4RS 4000

30 C/4RS 4000

30 D/4RS 3600

Clear code 112 Light transmission**% Solar transmission % Shading coefficient

40 56

0.63

67 76

0.87

67 76

0.87

67 76

0.87

67 76

0.87 K-value W/m2.K 1.5 1.9 1.9 1.9 1.9 Sound insulation dB 21 22 22 <22 22 Hail impact test Bullet 20 mm Velocity m/sec

>21 >21 >21 >21 >21

*Typical values only **Light transmission value may vary by plus or minus 3%

Value measured on injection-moulded laboratory sample.

4.7.3 SOLAR CONTROL PROPERTIES Temperature Increase inside the Building Sunlight entering the building heats the air both directly and through absorption by the framework, furniture, etc., and is released as infra-red energy. In combination with the insulating properties of Lexan Thermoclear sheet, this prevents heat escaping faster than it is created causing a temperature increase – the so-called ‘greenhouse effect’. The temperature can be controlled by venting, often in combination with specially tinted Lexan Thermoclear sheet, by Lexan Thermoclear Venetian Grades and Lexan Thermoclear Solar Control SC/IR. Solar Control Transparent grades of Lexan Thermoclear sheet have excellent light transmission, between 38 and 83% depending upon thickness. However, for buildings in hot climates or with south facing aspects, Lexan Thermoclear sheet is available in translucent grades of bronze, grey, blue, green, opal white, Lexan Thermoclear Solar Control sheet and Lexan Thermoclear Venetian sheet with screen printed white stripes on the non UV protected side. These grades significantly reduce solar heat build-up, helping to maintain comfortable interior temperatures.

The specially tinted sheet, Lexan Thermoclear Venetian sheet and Lexan Thermoclear Solar Control sheet cuts down the brightness of sunlight to a pleasing level and reduces air conditioning costs in the summer. Lexan Thermoclear Solar Control IR (SCIR) sheet does not significantly, like most other solar control products, block or reflect sun light but absorbs that part of the light spectrum which creates solar transmission. Lexan Thermoclear SC/IR is an excellent candidate for those applications where there is a need for high light transmission together with low solar transmission. Table 4.4: Total Solar Transmission* in % Solar Control IR (LTC-IR)

Structure Grade Name

Gau

ge (m

m)

Wei

ght (

kg/m

2)

Rib

dis

tanc

e (m

m)

ISO

100

77 U

V

alue

*(W

/m2K

)

LT

** S

C IR

Gre

en (%

)

LT

** S

C IR

Blu

e (%

)

LT

** S

C IR

Gre

y (%

)

TST

#SC

IR G

reen

(%)

TST

# SC

IR B

lue

(%)

TST

# S

C IR

Gre

y (%

)

SC¶

SC IR

Gre

en (%

)

SC¶

SC IR

Blu

e (%

)

SC¶

SC IR

Gre

y (%

)

2-Wall 2UVIR6/2RS13 6 1,3 6 3,56 66 60 0,69 2UVIR8/2RS15 8 1,5 10 3,26 65 61 0,70 2UVIR10/2RS17 10 1,7 10 3,02 65 52 20 60 58 42 0,69 0,67 0,48

3-Wall 2UVIR16/3TS27 16 2,7 20 2,27 55 36 52 49 0,60 0,56 3-Wall X-structure 2UVIR16/3X29 16 2,9 16 2,10 46 29 22 45 32 30 0,52 0,37 0,34

5-Wall 2UVIR10/5RS175 10 1,75 8 2,39 48 48 0,56 2UVIR20/5RS33 25 3,3 18 1,77 46 46 0,53

5-Wall X-structure 2UVIR20/5X32 25 3,2 20 1,69 24 37 0,51

2UVIR32/5X38 32 3,8 20 1,32 36 20 12 42 35 30 0,49 0,40 0,34 6-Wall 2UVIR16/6RS27 16 2,7 20 1,84 42 45 0,52

* U-values based on Sabic calculated values according ISO 10077 (EN673) ** LT (Light Transmission) measurements according ISO 9050 (EN 410) on 600x600mm samples # TST (Total Solar Transmission) measurements according ISO 9050 (EN 410) on 600X600mm samples “ Shading Coefficient (SC): The ratio of the total solar radiation transmitted by a given material to that transmitted by normal

3mm glass, whose light transmission is 87%. SC=%TST/87 Solar Heat Gain The solar radiation reaching the sheet is reflected, absorbed and transmitted. The greatest proportion is transmitted and the total solar transmission (TST) is the sum of the direct transmission (DT) and the inwardly released part of the absorbed energy (A). Table 4.4 lists the solar control properties of the Lexan Thermoclear sheet range and Lexan Thermoclear Venetian products.

4.7.4 GLAZING SYSTEMS Dry glazing systems This selection illustrates some glazing proposals using commercially available profiles which have proven to be successful in combination with Lexan Thermoclear sheet. Situations may occur where sheet expansion exceeds sealant limitations and, often for aesthetic reasons, this type of ‘dry’ glazing system provides an ideal solution. The advantage of dry systems is that the rubber gaskets snap-fit into the glazing strips which then allow free movement of the sheet during expansion and contraction. See figures 4.7 and 4.9. WARNING! Do not use PVC gaskets. Due to the migration of additives from soft PVC, the Lexan Thermoclear sheet can be chemically affected resulting in surface cracks or even sheet breakage. A wide range of easy to use glazing bars and fixing accessories, designed specifically for glazing Lexan Thermoclear sheet, is available from most of the approved Lexan Thermoclear distributors and specialized installers. Wet glazing systems This type of installation system is mainly used in small domestic type applications, carports, warehouses, conservatories and other glass replacement situations. With standard metal profiles or wooden sections, in combination with glazing tapes and glazing compounds, many different configurations are possible. See figures 4.8 and 4.10.

When using glazing compounds it is essential that the sealant system accepts a certain amount of movement, to allow for thermal expansion, without loss of adhesion to the frame or sheet. Silicone sealants are generally recommended for use with Lexan Thermoclear sheet, but it is strongly advised when using sealing compounds to check compatibility before use. Care should be taken not to use amine or benzamide curing silicone sealants, which are not compatible with Lexan sheet and result in crazing, particularly when stress is involved. Sheet glazing guidelines Wet Glazing Dry Glazing

Figure 4.7

Figure 4.8

Figure 4.9 : Neoprene, EPT or EPDM rubber gasket

Figure 4.10

Do’s

Clean the window frame. Remove old putty or broken glass, if necessary. Measure the sheet edge engagement area (± 20 mm) and internal window frame dimensions, i.e. the space into

which the Lexan Thermoclear sheet will be fitted Calculate the sheet size, allowing clearance for thermal expansion (3 mm per linear meter) Select the right thickness to fulfil loading requirements, K-value, etc. Clamp the Lexan Thermoclear sheet to a support table to avoid vibration and rough cutting Cut the sheet to the required size, using a standard electric circular or jig saw Blow away saw dust build-up in the channels with clean compressed air Remove any sharp edges and irregularities from the sheet Peel back approximately 50 mm of the masking film from all edges of the cut sheet on both sides Carefully select the sealing tape appropriate to the glazing application Seal the top and the bottom sheet channels with impermeable and/or venting tape, f.i. Multifoil G3629 / AD

3429. Please refer to the processing instructions provided by the sealing tape supplier. In case of venting tape, and to allow condensation drainage, apply an alu closure profile with drainage

possibilities or apply some single sided self-adhesive glazing tape as distance holder between the venting holes For wet glazing apply single sided self-adhesive glazing tape or rubber profile to both window frame and bead For dry glazing, snap-fit compatible neoprene rubber gaskets in place in the support profile as well as in the

clamping cover profile Insert the Lexan Thermoclear into the window frame Lexan Thermoclear sheet must always be installed with the ribs running vertically. The UV protected surface

should always face outwards Fix the window bead or the clamping cover profile in place For wet glazing apply and approved silicone sealing compound, such as Multisil / Silpruf between the sheet and

the window frame / bead Remove all masking film immediately after installation Clean the window carefully with warm soapy water and with a soft cellulose sponge or wool cloth

Don’ts

Do not use plasticized PVC or incompatible rubber sealing tapes or gaskets Do not use Amine, Benzamide or Methozy based sealants Do not use abrasive or highly alkaline cleaners Never scrape Lexan Thermoclear sheet with squeegees, razor blades or other sharp instruments Do not walk on Lexan thermoclear sheet at any time Do not install Lexan Thermoclear sheet with damaged tapes Do not clean Lexan Thermoclear sheet in hot sun or at elevated temperatures Benzene, gasoline, acetone, carbon tetrachloride or butyl cellosove should never be used on Lexan Thermoclear

sheet. 4.7.5 SEALING GUIDELINES Edge Sealing In all cases Lexan Thermoclear sheet should be mounted with the ribs running downwards to assist condensation water drainage. Algae growth, in the form of a green deposit inside the sheet channels, may occasionally be a problem. It is the result of permanent condensation inside the channels due to particular temperature conditions. Since moisture build-up and dust/insect contamination inside the channels can be major problem, one of the most important aspects of installation is edge sealing, particularly of the open-ended channels. There are several techniques that can be adopted to significantly reduce contamination, the choice depending largely on the prevailing environmental conditions. Sealing Tape It should be noted that the tape delivered on Thermoclear sheet is for protection, during transportation and storage, only and is not an impermeable sealing / installation tape. This tape should be replaced prior to installation with a tape as described below. Before taping, approximately 50mm of the masking should be removed from all sheet edges. The remaining masking should be removed only when installation is completed.

The tape should have good weathering resistance, without loss of long-term adhesion or mechanical strength. The tape should have good resistance to tearing and other damage during installation and handling. In close co-operation with the company Multifoil, an anti-dust impermeable tape G3600 and an anti-dust venting

tape AD3400 / AD4500 have been developed. Multifoil will provide within Europe a 10 Year Guarantee on the operation of the tapes.

The following Guidelines are recommended to minimize sealing and contamination problems:

Ensure that all sheet edges are smooth and rounded before applying the tape. All channels should be blown free of dust before sealing. Ensure tape is completely covered by glazing profiles, flashings, end closures, etc. No tape should be left exposed

when installation is complete. Replace any damaged tape before final installation. Recommended sealing tapes for glazing Lexan Thermoclear sheet are available from most approved Lexan

Thermoclear distributors and specialised installers. Chemical resistance Lexan Thermoclear sheet has been successfully used in combination with many building materials and glazing compounds. Taking into account, the complexity of chemical compatibility, all chemicals which come into contact with polycarbonate should always be tested in the particular application. For sheet products, the most common materials are sealants, gaskets and the various cleaning media. Chemical compatibility testing is an on-going process at SABIC Innovative Plastics Structured Products and many standard products have already been tested. A complete list of recommended cleaners, gaskets and sealants is available upon request. However, a shortened list of some of the more common compounds is shown below. When using glazing compounds it is essential that the sealant system accepts a certain amount of movement to allow for thermal expansion, without loss of adhesion to the frame or sheet. Silicone sealants are generally recommended for use with Lexan Thermoclear sheet, see table 4.5. It is strongly advised when using sealing compounds to check compatibility before use.

Table 4.5 Recommended Sealants

Sealant Supplier Silpruf SABIC Innovative Plastics Bayer Silicones

MultiSil SABIC Innovative Plastics Bayer Silicones Compatible Neoprene, EPT or EPDM rubbers with an approximate shore hardness of the A65 are recommended, and compatibility reports for different rubber types are available upon request.

Table 4.6 Recommended gasket systems

Gasket type* Supplier EPDM Chloropene, RZ4-35-81 Helvoet

EPDM 4330, 4431, 5530, 5531

Vredestein

EPDM 3300/670, 64470 Phoenix

* More grades available In case of doubt about any aspect of the chemical compatibility of the Lexan Thermoclear sheet range, always consult your nearest SABIC Innovative Plastics Structured Products sales office for further advice.

4.8 OTHER PLASTICS 4.8.1 PMMA (polymethtyl methacrylate) More commonly referred to as acrylic, has been available for more than sixty years. It is one of the most versatile plastic polymers and can be converted into either a finished or semi-finished product. In sheet form it can be manufactured by one of three processes, the most established of which cell is casting. In this form it was first manufactured in Britain and Germany in the early 1930’s. Its light weight, high transparency, strength and ease of formability made it an ideal material for aircraft glazing. It is still used today for high performance military and commercial aircraft glazing as well as a diverse range of other products ranging from leaflet holders to complex engineering components. Although it is available in a wide range of colours it is a naturally clear polymer and competes in certain applications with other naturally clear polymers such as PVC, polycarbonate, PETG and polystyrene. However, all these polymers are very different in their chemistry, properties and working characteristics. To ensure the right choice of material is made for a specific application and that it is properly fabricated, a good working knowledge of these polymers and their respective fabrication techniques is essential. Methyl methacrylate (MMA) is a monomer with a water clear appearance. It is flammable and has a distinctive smell. Some acrylic cement is based on MMA and fabricators using these products will be exposed to its vapours. Although it is not known to be a carcinogen, like all chemical products it must be used in accordance with the data sheets provided. To convert MMA monomer into a solid sheet it has to be polymerized. It is then referred to as polymethyl methacrylate, (PMMA) its true generic term. A more user friendly term however is acrylic. In sheet form the polymer can be made by several methods of cell casting, band or continuous casting and extrusion. The Basic Chemical Structure of Acrylic Chemically all acrylic sheet is basically the same, but the processes used to manufacture the sheet will affect the molecular weight of the polymer and this will determine the performance characteristics of the material during fabrication as well as its service life. Cell cast acrylic sheet will differ from one manufacturer to another as will extruded acrylic sheet, and cell cast sheet will behave very differently to extruded sheet. Get it wrong and you’re in trouble. To be able to understand why the properties and characteristics of acrylic are important when choosing a material it helps to understand the basic structure of the polymer. The composition of water is made up of billions of molecules and is a very simple construction containing two hydrogen and one oxygen atoms. It has the formula H2O. Each molecule is independent and can move freely in relation to the other molecules surrounding it, allowing it to assume a liquid state. MMA monomer assumes a similar liquid state to water but it has a very different chemical composition. A MMA molecule comprises of five carbon, eight hydrogen and two oxygen atoms and has the formula CH2; C(CH3).CO.OCH3. It’s like comparing the size of a tennis ball to a marble. Because extruded acrylic sheet has slightly different handling characteristics to cell cast acrylic, it cannot be worked in exactly the same way as cell cast, even though the same basic principles of fabrication apply. This may cause some problems for fabricators new to extruded sheet, and changes the technique will have to e adopted if successful fabrication is to be achieved. The table below gives a comparison between cell cast and extruded sheet using the basis that 10 would be the maximum achievable value with acrylic sheet.

VALUE CELL CAST EXTRUDED RATING CAST EXT

Cost Competitive Slightly lower 10 9 Thickness Thick block possible Limited to 15/20 mm 10 2.5 Colours Wide range Restricted 10 0.5 Sizes Limited by glass sizes Up to 1,85 metres wide & 6 metre lengths 10 10 Fire Rating Supports combustion Supports combustion – drips 10 5 Notched impact Impact sensitive to notches Twice sensitivity of cast 10 5 Craze Resistance High Lower by 65 – 70% 10 3 Chemical Resistance Good Lower 10 9 Outdoor Weathering (Yellowness)

Excellent Excellent 10 10

Outdoor Weathering (Mechanical)

May craze ** High risk of crazing ** 10 4

Thickness Tolerance Poor Good 5 10 Vacuum Formability Fair Excellent 6 10 Shrinkage 2 – 3% Bi – Axially Average 5% in line of extrusion only 10 7 Optical Quality Very good Good 10 9 **Crazing may appear as a result of environmental stresses. Poor construction and installation will exacerbate the effect.

Acrylic Sheet Variants Acrylic sheet is available from a number of different manufacturers throughout the world. Although the basic product offered is clear cell cast and extruded sheet, there are also many variants available from the majority of manufacturers. Below is a list of the main categories available for cell cast sheet, some of which may also be available in extruded sheet.

Size options. Thicknesses from 1mm to in excess of 100mm. Opals (whites of differing light transmittance). Colours with variable transmittance where transmittance decreases as thickness increases, or constant

transmittance where transmittance remains constant irrespective of thickness. Tints. Surface finish – there are many different grades in this category some of which are quit obscure. Various grades with enhanced impact resistance and ease of formability.

Applications Acrylic sheet is a versatile material that has been used for many applications since its conception in the 1930’s. For many of those applications nothing better has been found. The following list gives some of the applications for which acrylic sheet is still used:

Advertising, promotional and shop signs – Internally and externally illuminated – (for some locations check local fire regulations)

Aircraft glazing – special grade Aquaria Architectural glazing. Subject to local fire regulations. Cold storage cabinet dividers (impact strength improves as temperatures drop below 0°C) Decorative models Decorative (desktop/table top) furniture Decorative screens and panels Decorative furniture Domestic, medical, spa and other types of baths and washbasins. Special grades available. Engineering component Engineering models Food trays and display dishes – (observe food contact regulations) Jewellery Laboratory/photographic water and chemical tanks Leaflet holders Lenses – (contact and intra ocular require a special grade) Lighting – industrial, street and domestic Motorway noise screens – special grade Office desk utilities Photograph frames Point of sale display units Pressure vessel and other observation panels and screens Theatre and TV set furniture Vehicle, boat and other transport glazing

The Main Working Properties of Acrylic Sheet The properties of synthetic polymers are determined by their structure, which is dependent on the chemistry and type and quality of polymerization. Properties give a guide to the way in which materials will perform when used in specific applications. It is therefore important that the sales person, buyer, specifier or designer has some knowledge of the properties of the materials they work with. Properties are determined by a number of different tests and measurements designed to give an indication of the expected performance parameters for a material during its service life. It should not be assumed that all makes of one generic type of polymer will be exactly the same as another and certainly they will differ greatly between generic types. In addition to the differences between cell cast and extruded acrylic sheet, which exist as a result of varying polymer lengths, each manufacturer uses slightly different formulations and processing methods so the properties of acrylic sheet will vary slightly from one manufacturer to another. It is often assumed that the property values quoted by a manufacturer for their product will hold true under all circumstances. Although that may be true in most cases, much depends on how well they acrylic sheet has been fabricated. Crazing, for example, occurs because a property value has been exceeded.

Incorrect heating during thermoforming and line bending can cause changes to the chain structure of the material and degrade other additives. In both cases property values will have been changed and this may lead to premature failure of the finished product in service. All synthetic polymers have limitations governed by both their properties or limitations of the manufacturing processes and these will become apparent in the following pages. The property values given in this document are based on average values from several manufacturers and are intended only as an approximate guide. Abrasion resistance. Approximately 40% less than glass and comparable to aircraft grade aluminium. Surface abrasions can be polished out and high gloss restored. Chemical resistance. Resists attack from many common alkaline chemicals. Chlorinated solvents will cause dissolution. Some solvents and alcohols will contribute to crazing. Density (weight). The density of acrylic sheet is 1.194 g/cm3. It is about half the weight of glass and makes acrylic sheet an ideal material for light weight applications such as boat and aircraft glazing. Flammability. Acrylic sheet is flammable. High molecular weight cell cast sheet supports combustion and burns with a distinctive crackle. Very little smoke or harmless combustion products are produced and its long chain structure prevents dripping. Extruded sheet burns in much the same way as cell cast except that it burns quietly and has the disadvantage of dripping, which increases the risk of fire propagation to other areas. In the UK good quality cell cast sheet will show a class 3 rating when tested in accordance with BS 476 pt. 7 surface spread of flame test. Extruded sheet will fall into class 4. The use of class 4 materials within the area of petrol station forecourts in the UK is prohibited. Flexural strength. One of the most rigid plastics making it suitable for applications exposed to high loads i.e. Water tanks, roof lights and large area signs. Impact resistance (unnotched). Approximately five time that of plate glass. Both cast and extruded sheet can be impact modified, but his may impair some of the other properties.

Impact resistance (notched). Notches will reduce the impact strength of cell cast and extruded acrylic sheet whether it is impact modified or not. Extruded sheet has approximately twice the notch sensitivity of cell cast. Impact resistance (effect of notching) Impact resistance can be measured in different ways. Whichever method is used, the results can only give an indication of how the impact resistance of one material compares with that of another material tested under the same conditions. The impact resistance figures quoted are for guidance only. Because of the many factors which influence impact performance it is unlikely that they will give a true indication of how the material will perform after fabrication and in service. Bi-axially stretched sheet, for example, will have greater impact strength than unstretched sheet of similar thickness. The factor that most affects impact strength is notches which occur either as a feature of design or, more commonly, from the fabrication process. A notch point can vary from a surface scratch to a drilled hole or a chipped edge to a ninety degree corner cut out. During machining operations notches can be prevented by ensuring that the cutting tools are in a well maintained condition and that the correct machining parameters are adhered to.

From a design point of view a radius is a better proposition than a sharp corner. Radii spread stresses, induced at a notch point when the material is deflected under load, and reduce the risk of failure at the notch point.

Light transmittance. At 92% acrylics have a higher light transmittance than other plastics and glass (87%). Unlike other plastics, loss with large increases in thickness is very low and there is less deterioration from outdoor exposure. Moisture absorption. Like most materials, acrylic sheet is hygroscopic and will absorb up to 2.2% of moisture under certain circumstances. Levels of less than 0.8% are, however, more likely in normal everyday storage and use. Moisture content alters with changes in temperature and humidity; it will induce stress into acrylic sheet and affect its dimensional stability. The effect of these changes should be considered in applications where acrylic sheet is to be fitted into a frame, bonded to dissimilar materials or when bonding cell cast to extruded sheet. The polyethylene masking, commonly used to protect the surface of acrylic sheet, will retard moisture absorption but will not prevent it. The masking film should always be removed before final installation of the finished product. Extruded sheet may need pre-drying before it can be formed.

Temperature performance range. The long term service temperature range for acrylic sheet is between +80°C and -40°C. the most brittle state within that range is 0°C to +20°C, which makes acrylic an ideal material or low temperature applications. Thermal expansion. Temperature variations will cause dimensional changes to occur in acrylic sheet. To avoid high stresses and distortion in the final application, allowances must be made. The formulae for calculating the coefficient of linear thermal expansion varies from one generic type to another but the average figure is in the region of 7.3 X 10-5 cm/cm °C. For general applications the table below can be used to determine the expansion/contraction allowances. In outdoor applications such as signs an additional allowance of approximately 1.5 to 2mm per metre length must be made to compensate for the absorption of moisture.

EXPANSION ALLOWANCES FOR ACRYLIC SHEET IN mm/METRE LENGTH

Temperature °C 1 2 5 10 20 30 40 50 60 70 80 90 100 Expansion 0.07 0.15 0.39 0.78 1.56 2.34 3.12 3.9 4.8 5.46 6.24 7.02 7.8

Thickness tolerances. Cell cast acrylic is prone to wide thickness variations across the area of the sheet. The larger the area and the thinner the cast the more difficult it is to control thickness tolerances and variations of up to 20% may be experienced. As sheet thickness increases, thickness tolerances improve slightly. Sign makers are particularly prone to the effects of thickness variations when using coloured sheet to construct facia panels. With certain colours a change in hue may be observed when viewed by transmitted light at the point where two panels butt together. Even very small variations in thickness can produce this effect. Thickness tolerances of extruded sheet are generally superior to those of cell cast. Outdoor weathering (yellowing). The outdoor weathering performance of good quality unmodified clear acrylic sheet is outstanding in all climates and should give in excess of ten years and possibly more with very little discolouration. Outdoor weathering (general). Colour fading will occur with pigmented sheet. Over a two or three year period impact modified sheet may suffer loss of impact strength and display signs of discolouration. Due to thermal expansion and contraction, moisture absorption and flexure inflicted by climatic changes, stresses will be induced into the material. This may lead to crazing and subsequent failure of the finished product.

4.8.2 PVC CLEAR (POLYVINYL CHLORIDE) General information PVC Clear is the name for transparent, extruded sheets based on uPVC, which contains no softeners, in accordance with DIN 7748. The sheets are covered both sides with a self-adhesive protective film to protect them from surface damage. Characteristic properties of clear PVC are:

Excellent rigidity and dimensional stability Self-extinguishing (flame retardant up to 4 mm according to DIN 4102, 81) good chemical resistance to acids,

alkalis and salt solutions High light transmission and transparency Excellent electrical insulating properties. Odourless and non-toxic (However in general only very specific grades satisfies recommendation of the BgW)

Distinguishing characteristics Standard clear PVC Standard, transparent, shockproof rigid PVC based on DIN 16927, sheet 1. Excellent rigidity and transparency make this material ideal for many applications. As other grades with specific properties are available from a number of manufacturing extruders, please check with these suppliers for other characteristics. Applications PVC clear is an ideal material for many applications. The different versions available are specially designed to satisfy different requirements and combine the advantages of rigid PVC (uPVC) with maximum translucency. The high chemical resistance of this material is a particular feature. It can be used economically for chemical and process engineering applications. The following can be regarded as typical areas where clear PVC can be used:

Pipe systems, e.g. in the chemical and food industry panelling Switch boxes Vacuum forming parts DIY File boxes Shop window displays Exhibition constructions sing Advertising Lamp shades Stage sets TV studios Templates trays/dishes for distribution purposes Partitions

Clear PVC can also be used in installations where it is necessary to monitor the process, e.g. in general engineering and chemical engineering.

Table 4.7 - Material characteristics PVC Clear Test Standard Dimension Clear PVC Standard

Density DIN 53479 g/cm3 1.37 Tensile-E-Modulus DIN 53455 N/mm2 3200 Yield stress DIN 53455 N/mm2 72 Elongation at yield DIN 53455 % 3 Elongation at tear DIN 53455 % 11 Impact strength DIN 53453 kJ/m2 Without break Notched impact strength DIN 53453 kJ/m2 2 Indentation hardness H358/30 DIN 53456 N/mm2 140 Shore hardness D DIN 53505 - 83 Vicat softenino temperature 8/50 DIN 53460 K (OC) 345(72) Mean thermal longitudinal expansion coefficient DIN 53752 K.1 0.8 10.. Thermal conductivity” DIN 52612 W/mK 0,159 Dielectric strength ** Method K 20/P 50

DIN 53481 kV/mm 30

Spec. volume resistance Ring electrode

DIN 53482 Ohm .cm >10’5

Surface resistance Electrode A

DIN 53482 Ohm 10”

Material characteristics (Continue)

Test Standard Dimension Clear PVC Standard Tracking resistance Method KC DIN 53480 V >600

Dielectric constant at 300 – 1000 Hz At 3.105 Hz DIN 53483 - 3.0

2.9 Dielectric loss factor At 300 Hz At 1000 Hz At 3.105 Hz

DIN 53483 -

0.016 0.01 0.02

Measured on test specimen 10 mm thick measured on test specimen 1 mm thick The figures indicated are guide values and may vary according to the processing method c used to make the test specimen. Unless specified otherwise, these are average values measurements on extruded sheets 4 mm thick. These values cannot be automatically used for finished parts. The manufacturer/user should check the suitability of our materials for a specific application. Combustion behaviour

Standard Clear PVC is classified as a flame retardant material, class B1, in accordance with DIN 4102, part 1. The corresponding test reference Z – PA – 1112.810 is available for wall thicknesses up to 4mm. The ignition temperature is above 390º Celsius. The oxygen index is 40%. There are special grades which have been combustible – classified as a normally part, 4102 according to DIN, 82 class, and material 1. Check with manufacturers for availability.

Behaviour in outdoor use Standard clear PVC is not generally suitable for outdoor applications. However the stabilisation of standard clear PVC may be considered in individual cases depending on the conditions of use. Chemical resistance Clear PVC is chemically resistant to aqueous acids, alkalis and salts at ambient temperature. The same applies to alcohols, aliphatic compounds and many oils. Aromatic compounds and halogenated hydrocarbons, esters and ketones will etch the material. PVC is not resistant to very strong oxidizing agents; in this case, there is the risk of stress crack formation at welds and at cold and hot shaped positions. Mineral acids, such as, for example, sulphuric acid, nitric acid and hydrofluoric acid, will cause clear PVC to discolour within a relatively short period. Its translucency and, therefore, transparency, is then lost. Some clouding of clear PVC may occur, although the material is generally classified as “chemically resistant”; in this case, the transparency is automatically reduced, but is maintained to a certain degree. Water absorption Generally speaking, rigid PVC can absorb a certain amount of moisture, which is revealed by the formation of tiny blisters when it is heated up in the vacuum forming machine. In such cases, the material should be dried first for 12 hours at 55 DC in a circulating air oven; storage overnight is sufficient in the majority of cases. As a rule, provided that the sheets are stored in a dry place, pre-drying is not necessary. Light transmission Standard clear PVC has excellent optical properties. For example, the light transmission according to standard light C is 82% for 4 mm standard clear PVC 4.8.3 PET SHEET (Polyethylene Terephthalate Sheets) This polymer is a major development in the world of plastic sheets; Sheet Plastic has considered it important to include it in its current range of products to be offered to its customers. SHEETPET sheets have an excellent fire resistance (BS476: Part 7: Class 1Y) and they are self-extinguishing. They are safe to use with foodstuffs and are highly resistant to chemical agents and weathering. They save time and energy since they do not require pre-drying and can be quickly thermoformed. These sheets have a wide range of applications, from roof domes, rooflights and greenhouse glazing, to bus shelters and vandal proof glazing, signs, displays, trays and vending machine facias. An important new feature of certain thicknesses is the availability of the product on rolls. Different colours, or anti-UV treatment are available on demand.

STANDARD SPECIFICATIONS FOR PET RESIN

CODE UNIT VALUE PHYSICAL Density ISO 1183 g/cm3 1.34 MECHANICAL Tensile strength @ yield ISO 527 MPa 59 Tensile strength @ breakage ISO 527 MPa No breakage Elongabon @ breakage ISO 527 % No breakage Elasticity modulus in traction ISO 527 MPa 2,420 Resistance to flexion ISO 178 MPa 86 Charpy impact test with notch ISO 179 kJ/m2 (*) Charpy impact test ISO 179 kJ/m2 No breakage Rockwell hardness, M / R scale (*) / 111 Ball pressure hardness ISO 2039 MPa 117 OPTICAL Light transmission ASTM D-1003 % 89 Refractive index ASTM D-542 1.576 THERMAL Maximum Service temperature °C 60 VICAT Softening temperature (10 N) ISO 306 °C 79 VICAT Softening temperature (50 N) ISO 306 °C 75 Heat deflection temperature, HDT A U.8 MPa) °C 69 Heat deflection temperature HDT B (0.45 MPa) ISO 75-2 °C 73 Coefficient of linear thermal expansion ISO 75-2 x103 /°C <6 These data correspond to raw material values

CHEMICAL RESISTANCE

CHEMICAL PRODUCT BEHAVIOUR Satisfactory Regular Unsatisfactory

Mineral oil X Vegetable oil X

Acetone X Acetic acid X

Water X Turpentine X Ammonia X Detergents X

Ethanol X Petrol X

Glycerine X Methanol X Toluene X

REACTION TO FIRE

COUNTRY CODE CLASSIFICATION Great Britain BS 476; Part 7 IY

Germany DIN 4102.1 B1 France NFP 92-507 M2 Italy UNI 9177 Class 1

A NUDECPET safety file is available for any additional type of query. (*) Non-applicable

4.8.4 PET Properties Dimensional Stability to heat Articles manufactured with this product must not be continually exposed to temperatures above 60°C, depending on the application.

Ageing The UV component of sunlight causes degradation to all plastics in general. This degradation depends on the exposure conditions, in other words, on the actual duration of exposure to sunlight, the sheet inclination to the sun’s rays, temperature and humidity and on sunlight intensity (geographical coordinates). This degradation shows up as a progressive yellowing, a reduction in light transmission and loss of mechanical properties. PET sheets are not protected against the effects of sunlight, however, the actual material itself possesses a certain resistance to outside weather so that it can be used in exterior applications in locations where sunlight is of low intensity and does not permanently fall on the sheets. For exterior applications where the sheets are permanently exposed to ultraviolet light, a stabilized product, such as PETuv sheets, which are protected on both sides, are recommended. When used in exterior applications, the protective film must be removed immediately, since exposure to sunlight can cause permanent adhesion to the sheet. Chemical Resistance In general, PET sheets are able to resist most acids, alcohols, and salts, together with plastitfying agents. They are also resistant to hydrocarbons, such as xylene, mineral oils and petroleum. However, resistance to aliphatic hydrocarbons is limited. Similarly, PET sheets also resist the chemical attack of acid rain. Diesel engine exhausts fumes and air with a certain amount of salinity. Aromatic compounds can cause several reactions. Contact with food & sanitary use PET sheets (except the UV version) comply with the United States FDA (Food and Drug Administration) and the BGA (Bundes-gesundheitsamt, Germany) standards for contact with foodstuffs. PET is both odour and taste-free, making PET suitable for use applications where it comes into contact with toad, and in medical usage. PET sheets can be sterilized by gamma radiation or with ethylene oxide. 4.8.4.1 HANDLING Cleaning The sheets should be cleaned with a solution of warm water with a little neutral soap and rinsed with water employing a very soft sponge or chamois leather. Cutting/Sawing The common types of saws employed in wood or metal carpentry provide good results when sawing PET sheets: disc, band, sabre, jigsaw, hewing, and handsaw. Disc or band saws produce the best edges and can perform almost all cutting operations. Blade shape plays an important role in sawing plastics. It is recommended to employ a band saw with separated teeth because the empty space will facilitate the exit of the cut ships. The best results are obtained using teeth without any indication and also somewhat jumped. To prevent the plastic from cracking or melting, the blade must be very sharp and the guide should very close to the cut to prevent vibration. Die-stamping PET sheets can be satisfactorily die-cut with steel blades (up to 2mm). The blade has to be quite frequently replaced or sharpened. The dfHutting press must be adjusted so that he run completely traverses the plastic sheet and stops before blade cause any nicks. Polishing Pre polishing is required to eliminate any marking caused by the cutting disc. The following may be used:

Rotating rigid fabric discs with buffing paste Rotating soft fabric discs with buffing paste for the final finish flame polishing the edge is also possible with a

standard butane torch or a hot nitrogen welding torch, care should be taken of the exact distance between the sheet and the heat source and the passing speed. If the heat source is brought to close there is a danger of crystaUising-whitening the surface or the material may becoming too fluid:

Adhesives Because of the exceptional chemical resistance of PET sheets it is not possible to use adhesives with solvents. Among the recommended adhesives are the cyanacrylates, together with two component polyurethanes and epoxies. The following should be taken into consideration when selecting an adhesive:

Aesthetics of the finished joint Dilation and contraction with temperature changes

Fragility, rigidity and flexibility Alterability with respect to outside weather, where applicable Duration and useful lifetime Adhesive strength (adherence to the plastic)

Final usage requirements For perfect gluing of the surfaces to be joined, they must fit together well (without exerting force and without leaving any cavities and should also be smooth and unpolished. Certain adhesives with volatile components may contract during drying. This effect can be compensated by cutting the joint at an angle, thus leaving space to be filled with a slight excess of adhesive. Thermoforming Pre-drying, as required for polycarbonate, is not necessary. Time and energy savings:

Thermoforming temperatures between 120 and 150°C very high temperatures can reduce the impact strength of the material.

Mould temperature must not exceed 60°C It is recommended that heating time is reduced to avoid crystallisation.

Pet uses film to protect the surface from possible damage during production and transport. This protective film is not prepared to withstand high temperatures and must be removed prior to thermoforming or hot-bending 4.8.4.2 BENDING Cold bending PET sheets of less than 3mm can be cold bent using standard equipment as employed for metal sheets, such as presses or bending machines. The surface protection film should be left in place during the bending process in order to protect it from scratches. It is best not to employ excessive speed for bending since too must stress can cause the surface to break up. Bending with incandescent wire Standard two-side, incandescent wire bending equipment can be satisfactorily employed. Excessive wire temperature or is insufficient distance between the wire and the sheet can lead to slight crystallization (fine white misting) of the sheet surface. If this occurs, then the wire power should be reduced or the distance between the wire and sheet increased. In extreme cases, the wire can be replaced for one with a larger diameter in order to reduce the resistance and consequently its temperature. All PET products use film to protect the surface from possible damage during production and transport. This protective film is not prepared to withstand high temperatures and must be removed prior to thermoforming or hot-bending. Decoration Certain printing inks can display some difficulty in adhering to the PET due to its high resistance to solvents. The print film should be removed just prior to printing to prevent the surface from damage. PETg Sheet Polyethylene Terephthalate Copolymer Sheets

Application examples Signs and display construction Exhibition stands Machine guards Thermoforming sector Medical applications Orthopaedic applications Food industry

(handling trays, shop fittings) Building constructions

Displays, moulds, lettering, orthopaedic parts, toys, dispensing machines, cycling helmets, protective visors, containers … these are just some of the products that can be made from these sheets. Their main characteristics are their easy processing and resistance to impact and chemical agents, as well as their transparency and ductility. These characteristics mean SHEETPETg sheets can be easily fabricated, bent when cold (up to 2mm in thickness) and even cut using a laser beam. They come in different thicknesses and can be manufactured in different colours (like the present opal) and are available with anti-UV treatment or patterns.

Processing examples Thermoforming Screen printing Welding and bonding Nailing and screwing Punching and drilling Laser cutting Polishing Warm and cold bending Sawing Milling

PETg Apart from its crystal clear transparency, PETG sheet has impressive mechanical properties. PETg has extremely high impact strength, excellent vacuum forming properties and can be processed in a variety of ways. It is generally recognized as physiologically safe, making it suitable for applications in medical technology and the food processing industry. PETg sheets are resistant to many chemicals. Extremely high impact strength

shock resistant even at below zero temperatures (to -40°C) protection against vandalism economical by using thinner sheets

Easy to process

easy to punch and cut (up to 3mm) nailing is possible cold forming (up to 5mm) simple welding and gluing without loss of transparency laser cutting for reasonable mass production possible edges can be polished

Excellent vacuum forming properties

simple vacuum forming without loss of transparency excellent and uniform drawing behaviour minimized thinning good printing before thermoforming excellent definition of sharp edges and corners low machine operating costs due to short cycle times no need for pre-drying less waste due to a wide range of forming temperatures

Enables high-quality printing suitable for contact with foodstuff in accordance with

BgVV and FDA Suitable for sterilizing Flame retardant Weather resistant Environment-friendly

Density g/cm ISO 1183 1.27 Yield stress N/mm DIN EN ISO 527 52 Tensile-Ernodulus MPa DIN EN ISO 527 2000 Impact strength kJ/m DIN EN ISO 179 without break -40°C without break Transparency (sheet 4mm) 93% Notched impact strength kJ/M. DIN EN ISO 179 10 Shore hardness D 79 ISO868 Average thermal coefficient of elongation K’ DIN 53752 0,7 X 10-4 Fire behaviour DIN 4102 B1 till 6mm Dielectric strength kV jmm VDE 0303-21 16 Surface resistance 0hm DIN IEC 167 10 to power of 16 Temperature range c - 40 to + 65 Celsius Chemical resistance resistant to diluted acids, soaps, oils, alcohols & alkalis Physiologically acceptable ace. To sgw and FDA (USA) yes

chapter iv - aaamsa€¦ · wired glass or laminated wired glass or laminated glass with...

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