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Advanced Protective Textiles By Miss Shweta S. Joshi D.K.T.E.s Textile and Engineering Institute, Ichalkaranji

The definition of technical textiles adopted by the authoritative textile Terms and Definitions, published by the Textile Institute is textile materials and products manufactured primarily for their technical and performance properties rather than their aesthetic or decorative characteristics.1

12 main application areas of technical textiles are:

agrotech: agriculture, horticulture and forestry buildtech: building and construction clothtech: technical components of footwear and clothing

geotech: geotextiles and civil engineering hometech: technical components of furniture, household textiles indutech: filtration, conveying, cleaning and other industrial uses medtech: hygiene and medical mobiltech: automobiles, shipping, railways and aerospace oekotech: environmental protection

packtech: packaging protech: personal and property protection sporttech: sport and leisure

Protective and Safety clothing and textiles:

Textiles for protective clothing and other related applications are another important growth area which has attracted attention and interest somewhat out of proportion to the size and value of the existing market. The variety of protective functions that needs to be provided by different textile products is considerable and diverse. It includes protection against cuts, abrasion, ballistic and other types of severe impact including stab wounds and explosions, fire and extreme heat, hazardous dust and particles, nuclear, biological and chemical hazards, high voltages and static electricity, foul weather, extreme cold and poor visibility.1

In 2000, technical textiles accounted for about 25% of all textile consumption by weight ( David Rigby Associates, 2004). Protective textiles account for 1.4% of the total textiles with an estimated value of US$ 5.2 billion.

Consumption of protective clothing has increased linearly in the last 10 years and in 2010 it is expected that about 340,000 Te of protective clothing will be consumed, an increase of 85% over consumption in 1995. The Americans (mainly USA and Canada) have the highest consumption of protective clothing per annum at about 91300 Te followed by Europe 78200 Te and Asia with 61300 Te ( David Rigby Associates, 2004)

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Classification:

Personal protective textiles can be classified as:1

1. Fire Protection 2. Heat and cold protection 3. Chemical Protection 4. Mechanical impact protection 5. Biological Protection 6. Radiation Protection 7. Electrical Protection

In this paper we will go in detail of Radiation Protection and Chemical Protection.

Now, we will see one by one what it means.

Fire Protection: 2

It would have been impossible for humans to survive the primitive age without the use of fire. However, fire could be dangerous. Fire disasters occur frequently resulting in non-fatal and fatal casualties. In most of the fire accidents most frequently ignited materials were the textiles, especially upholstery and furnishings. It should, however, be noted that the main cause of death in a fire accident is not direct burning but suffocation due to the smoke and toxic gases released during burning.

Human tissue (skin) is very sensitive to heat. It is reported that, at 45Oc, the sensation of pain is experienced, and at 72 Oc. The skin is completely burnt. The purpose of fire protective clothing is to reduce the rate of heating of human skin in order to provide the wearer enough time to react and escape. The time that a wearer stays in flammable circumstances and the amount of heat flux produced are important factors for designing the protective stratagem. Under normal conditions, only 3-10 seconds are available for a person to escape from a [place of fire with a heat flux of about 130-330kW/m2. Fibers commonly used for textiles are easily burnt

Protective clothing designed for flame protection must have two functions, i.e. be flame-resistant and form a heat barrier. The latter is avery important factor if the wearer needs to stay near flames for a fairly long time. In fact the danger of burning lies with the parts of body not covered by clothing.

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Using inherently flame-retardant materials such as Kevlar, nomex, applying a flame-retardant finish or a combination of these methods are commonly used to make clothing and textiles flame retardant.

Heat and Cold Protection:

Basic metabolisms occurring inside our body generate heat that can be life saving or fatal depending on the atmosphere and circumstances that we are in. Normally, human bodies are comfortable to heat in a very narrow temperature range of 28-30Oc. In summer, we need the heat from our metabolic activity to be transferred outside as soon as possible, while in winter especially in extremely cold conditions, we must find ways to prevent the loss of heat from our body. Heat stress, defined as the situation where the body cannot dissipate its excess heat to the environment is a serious problem especially during physical working. 1,2

Basically, heat is transferred either as conductive, convective, radiant heat or a combination of these modes depending on the source of heat, the atmosphere the heat-absorbing material is in and the protection available against heat. Any heat transfer will have at least one of these modes and heat protection is the method to decrease or increase the rate of heat transfer. For protection from conductive heat, the fabric thickness and density are the major considerations, since air trapped between fibres has the lowest thermal conductivity of all materials. For protection from convective heat, the flame retardant properties of the fabric are important. As for radiant heat protection, metallized fabrics such as allumized fabrics are preferred, since metallized fabrics have high surface reflection and also electrical conductivity. Ideal clothing for protection from heat transfer are fabrics with thermoregulating or temperature adaptable properties. Phase change materials ( PCM) are one such example that can absorb heat and change to a high-energy phase in a hot environment, but can reverse the process to release heat in cold situations.

Now-a-days, a heat resistant woven fabric with an optional aluminized backing is disclosed. The fabric is particularly suited for heat resistant garments intended to resist radiant heat and heavy molten metal splashes in the temperature range of 2700OF-3000OF. The preferred fabric has core-spun yarns with a flame and high heat resistant filament core covered by a layer of flame retardant fibres consisting of at least 35% melamine. 3

Specifically designed protective clothing is necessary to survive and operate in temperatures below -30Oc. Such low-temperature conditions are aggravated in the presence of wind, rain or snow leading to cold stress that may be fatal. The most

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effective method of cold protection is to avoid or decrease conductive heat loss. Clothoing designed to protect from cold is usually multi-layered, consisting of a non-absorbent inner layer, a middle insulating layer capable of trapping air but transferring moisture, and an outer layer that is impermeable to wind and water.

Mechanical Impact Protection:

A. Ballistic protection: Ballistic protection is generally required for soldiers, policemen and general security personnel. Ballistic protection involves protection of body and eyes against projectiles of various shapes, sizes and impact velocities. Historically, ballistic protection devices were made from metals and were too heavy to wear. Textile materials provide the same level of ballistic protection as metals but have relatively lower weight and are therefore comfortable to wear.

High-performance clothing designed for ballistic protection dissipates the energy of the fragment/shrapnel by stretching and breaking the yarns and transferring the energy from the impact at the crossover points of yarns. The ballistic protection of a material depends on its ability to absorb energy locally and on the efficiency and speed of transferring the absorbed energy. Fibres like Kevlar, Ultra high modulus polyethylene are used for ballistic protection.

Ballistic protective Helmet

An Advanced design bomb suit and helmet that offers highest ballistic protection in the world. The suit is constructed from Kevlar with an outer antistatic cover of 50/50 Nomex/Kevlar and comprises of a jacket, crotch-less trousers, groin cup and rigid ballistic panels. The suit itself is light weight in comparison with other suits, with frond protection plates and this maneuverability reduces operator fatigue and increases operator effectiveness.3,4

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Other Impact protection:

Some examples are seat belts, air bags used in automobiles. Also, protective textiles used in sport are in knee braces, wrist braces, ankle braces, helmet and guards.

Biological Protection:

Most natural textile fibres such as wool, silk and cellulosics are subject to biological degradation by bacteria, dermatophytic fungi, etc. Textiles designed for biological protection have two functions: first, protecting the wearer from being attacked by bacteria, yeast, dermatophytic fungi, and other related microorganisms which cause aesthetic, hygienic or medical problems. Secondly, protecting the textile itself from

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biodeterioration caused by mold, mildew and rot-producing fungi and from being digested by insects and other pests.

Fabrics designed for microbial protection should act as barriers to bacteria and other microorganisms that are believed to be transferred from one location to another by carriers such as dust or liquids. Films generally have high barrier properties against microbes and chemicals. However, films when used with fabrics to provide antimicrobial properties make fabrics impermeable to airflow leading to heat stress and other physiological problems that may be fatal. New membrane structures called ‘perm-selective’ or breathable membranes have been developed that can prevent airflow through the fabric layer but have high water-vapour permeability. Using these membranes with fabrics provides effective protection from hazardous materials or microbes without causing heat stress.

Electrical Protection:

A. Electromagnetic Protection: Protection from electromagnetic sources is required because people who work close to power lines and electrical equipment have the possibility of being exposed to electric shocks and acute flammability hazards. Generally, rubber gloves, dielectric hard hats and boots, sleeve protectors, conductive Faraday-cage garments, rubber blankets and non-conductive sticks are used for electromagnetic protection.

B. Electrostatic Protection: Electrostatic charges accumulate easily on ordinary textile materials, especially in dry conditions. Charges once accumulated are difficult to dissipate. The dissipation of an electrostatic charge occurs through shocks and sparks which can be hazardous in a flammable atmosphere. Therefore, the presence of a static charge in textiles can be a major hazard in explosives, papers, printing, electronics, plastics, and the photographic industry.

The basic principle of making an antistatic garment is to decrease the electrical resistivity or the chance of electrostatic accumulation in a fabric.

Radiation Protection:

A. Nuclear Radiation Protection: Special clothing to prevent exposure to radiation is needed for people working in radioactive environments. Goggles, respiratory masks, gloves, and light weight protective clothing may be adequate for protection from some weak alpha, beta rays. Woven cotton, polyester/cotton or nylon/polyester fabrics with a twill and sateen weave are the major types of fabric forms used for nuclear protective clothing.

B. UV Radiation Protection: An appropriate amount of sun bath promotes the circulation of blood, invigorates the metabolism and improves resistance to various pathogens. Penetration of UVR into the top layer of the skin leads to damage in the lower layer and produces premature ageing of skin and other effects including roughening, blotches, sagging, wrinkles, squamous cells and basal cell cancer. Many people love sunbathing, thereby extending the long term risk to their health. Persons working in the open atmosphere are also prone to keratose, the precursor of skin cancer. Australia has high levels of solar UV radiation, mainly because of its geographical position; New Zealand, USA, Switzerland, Norway, Scotland, Britain and Scandinavian countries also have high melanoma rates.

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Unravelling the mysteries related to ultraviolet rays, their properties, and their effects on various living creatures has been a gradual process spanning to the duration of almost three centuries starting from the seventeenth century. 6 Terms such as near UV (290-400 nm), far UV (180-290 nm) and vacuum UV ( below 180 nm) have been coined by physicists based on the properties of the radiation. The term UVA represents the region 320-400 nm, the term UV B represents the region between UV C and UV A i.e. 290-320 nm and UV C region represents the region below 290 nm. The order of potency has been decided as UV C > UV B> UV A. The proportion of the UV region is about 5-6% of the total incident radiation, and the quantum energy of UVR is similar to the bond energies of organic molecules.

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Ultra-violet Protection factor The protection extended by the textile materials, accessories and sun screen lotions are denoted by different terminologies known as UPF and SPF. Risk estimates of unprotected skin, protected skin and UPF are given by the following formulae: Risk unprotected= ∑ SλAλ∆λ Risk protected= ∑ SλAλ∆λTλ

UPF= risk unprotected / risk protected

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occurs upon exposure to sunlight. Triazine class-hindered amine light stabilizers are used in PP to improve the UV stability. The addition of HALS to 0.15% weight is sufficient to improve stability substantially. High-energy UV absorbers suitable for PET include derivative of o-hydroxyphenyl diphenyl triazine, suitable for dye baths, pad liquor or print paste.

UV absorbers have refractive indices of about>2.55, by means of which maximum covering capacity and opacity is achieved. The presence of inorganic pigments in the fibres results in more diffuse reflection of light from the substrate, and provides better protection.6TiO2 added in the spinning dope for matt effects in the fibres also acts as a UV absorber. Titanium dioxide and Ceramic materials have an absorption capacity in the UV region between 280 and 400 nm, and reflects visible and IR rays, these absorbers are also added as dope additives.

Many commercial products and processes have been developed to produce fabrics with a high level of UPF using various dope additions and topical applications for almost all types of fabrics. Most of the commercial products are compatible with dyes and other finishing agents applied to the textile materials, and these agents can be applied using simple padding, the exhaust method, the pad-thermofix and the pad-dry-cure methods.7

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Textile Materials and UV Protection:

Sun Protection involves a combination of sun avoidance and the use of protective garments and accessories. Reducing the exposure time to sunlight, using sunscreens and protective clothes are the three ways of protection against the deleterious effects of UV radiation. Textile materials and accessories are largely used for UV protection. UV protection through textiles include various apparels, accessories such as hats, shoes, shade structures such as umbrellas, awnings, and baby carrier covers and the fabric materials to produce these items.

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Dyeing and Finishing: Depending upon the type of dye or pigment, the absorptive groups present in the dyestuff, depth after dyeing, the uniformity and additives, the UV protection abilities of the textile materials are considerably influenced.8 In a given fabric, higher transmission of UV radiation is observed in the case of bright fibres ( viscose) than dull fibres.9 A protective effect can be obtained by dyeing or printing, which is better than using heavyweight fabrics which are not suitable for summer conditions. Darker colours of the same fabric type ( black, navy, dark red) absorb UVR much more strongly than the light pastel colours for identical weave with UPF, in the ranges of 18-37 and 19-34 for cooton and polyester respectively.9 Some direct, reactive and vat dyes are capable of giving UPF of 50+. 10,11 Some of the direct dyes substantially increase the UPF of bleached cloth, which depends on the relative transmittance of the dyes in the UV B region.

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which plays an important role in skin disease.

sun burn in vivo. The preparation of the fabric prior to the UV transmission test includes the exposure of specimen to laundering, simulated sunlight and chlorinated pool water, and to present in a state that simulates the conditions at the end of two years of normal seasonal use, so that the UV protection level finally stated on the label estimates the maximum transmittance of the garment fabric during a two-year cycle.

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UV Protection Care Lebelling Initiatives for developing standards related to UV protection started in the 1990s, and standards related to the preparation of fabrics, testing and guidance for UV protection labeling have been formulated by different agencies.12 Care lebelling similar to fabric and garment care labels has been developed for UV protection, and standard procedures have been established for the measurement, calculation, labeling methods and comparison of label values of textile products.Below table shows the various grades and the related protection factors for the textile materials.

Standards for UV Protective Textiles:

AS/NZS 4399 ( Austalia/ New Zealand) As per this standard, Label UPF is calculated as per detailed procedure in the standard. The calculated label UPF is the mean sample UPF minus the standard error of the sample UPF, the result of which should be rounded down to the nearest multiple of 5. When the calculated label UPF value is greater than the lowest UPF value for an individual specimen, then the UPF value to be placed on a textile should be the UPF value of the specimen with the lowest UPF value, which is then rounded down to the nearest multiple of 5. No textile is given a UPF rating greater than 50. As per the standard, calculated UPF values of 40 -50+ classifes Excellent UV protection category.

UPF values greater than 25 but less than 40 classifies Very good UV protection. And those with calculated label UPF values higher than 15 but less than 25 classifies Good UV protection category. A textile must have a minimum UPF of 15 to be rated as UV protective. 1,13

Europe The European standard EN 13758-1 strives to overcome many of the drawbacks of the AS/NZ 4399 standard by recommending that only textiles with UPFs 30+ be labeled as sun protective clothing. It is reasoned that a UPF of 30+ will be robust to accommodate the effects of stretch, wetness, wear and use.Ultraviolet protective clothing complying with this standard must be permanently marked with the number of the European standard and with the designation ‘UPF+’36.1,13

Chemical Protection

A number of countries around the world have the capability to use chemical weapons. In fact, within the past decade, several events have been well documented where chemical weapons were used in armed conflict, most notably during the Iran-Iraq War. The major application of protective clothing is for protecting the soldiers from the war field hazards. One such important hazard is chemical hazard which affects the human based on its characteristics and mode of entry. To overcome this problem we normally

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use chemical protective clothing and their property depends on the end use. The routes of chemical entry into the human body are oral, respiratory, and dermal. Of these three main routes, the dermal exposure is considered the primary mechanism of chemical entry through human body. While considering the entry of chemical through respiration to prevent this it is essential to consider the respiratory mask as an essential part of chemical protective clothing. It has been reported that 90% of all occupational allergic contact dermatitis was found on the back of the hands and the fore arms. However contact dermatitis among homemakers occurred in almost 50% of the cases on the palms. Where as 15% of the time it affected the back of hands and fingers. The location on body affected by occupational contact is shown in the figure (Refer Fig 1.1). This makes clear that most of workers are affected by chemicals used in industries and work areas.5

Chemical protective clothing (CMC) should be considered the last line of defense in any chemical-handling operation and every effort should be made to use less hazardous chemicals where possible, or to develop and implement engineering controls that minimize or eliminate human contact with chemical hazards.

Protective chemicals cannot be made generic for all chemical applications, since chemicals vary in most cases and a particular CPC can protect only against a limited number of specific chemicals. Important considerations in designing chemical protective clothing are the amount of chemical penetration, breakthrough time for penetration, liquid repellency, and physical properties of the CPC in specific chemical conditions.

Chemical Protective clothing can be categorized as encapsulating or non-encapsulating based on the style of wearing the clothing. The encapsulating system covers the whole body and includes respiratory protection equipment and is generally used where high chemical protection is required. The non-encapsulating clothing is assembled from separate components and respiratory system is not a part of the CPC.

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Classification of chemical protective clothing:

1. Fully encapsulating suits; Nonencapsulating suits; Gloves, boots, and hoods; Firefighter’s protective clothing; Proximity, or approach clothing; Blast or fragmentation suits; and Radiation-protective suits. 5,12

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The environmental protection agency (EPA) in the united states classifies protective clothing based on the level of protection from highest to normal protection. CPC is rated for 4 levels of protection. Levels A,B,C,,D from highest protection to normal protection.

LEVEL A: Vapor protective suit (meets NFPA 1991) Pressure-demand, full-face SCBA Inner chemical-resistant gloves, chemical-resistant safety boots, two-way radio communication OPTIONAL: Cooling system, outer gloves, hard hat Protection Provided: Highest available level of respiratory, skin, and eye protection from solid, liquid and gaseous chemicals. Used When: The chemical(s) have been identified and have high level of hazards to respiratory system, skin and eyes. Substances are present with known or suspected skin toxicity or carcinogenicity. Operations must be conducted in confined or poorly ventilated areas. Limitations: Protective clothing must resist permeation by the chemical or mixtures present. Ensemble items must allow integration without loss of performance. LEVEL B: Liquid splash-protective suit (meets NFPA 1992) Pressure-demand, full-facepiece SCBA Inner chemical-resistant gloves, chemical-resistant safety boots, two-way radio communications Hard hat. OPTIONAL: Cooling system, outer gloves Protection Provided: Provides same level of respiratory protection as Level A, but less skin protection. Liquid splash protection, but no protection against chemical vapors or gases. Used When: The chemical(s) have been identified but do not require a high level of skin protection. Initial site surveys are required until higher levels of hazards are identified. The primary hazards associated with site entry are from liquid and not vapor contact. Limitations: Protective clothing items must resist penetration by the chemicals or mixtures present. Ensemble items must allow integration without loss of performance. LEVEL C: Support Function Protective Garment (meets NFPA 1993) Full-facepiece, air-

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purifying, canister-equipped respirator Chemical resistant gloves and safety boots Two-way communications system, hard hat OPTIONAL: Faceshield, escape SCBA Protection Provided:. The same level of skin protection as Level B, but a lower level of respiratory protection. Liquid splash protection but no protection to chemical vapors or gases. > Used When: Contact with site chemical(s) will not affect the skin. Air contaminants have been identified and concentrations measured. A canister is available which can remove the contaminant. The site and its hazards have been completely characterized. Limitations: Protective clothing items must resist penetration by the chemical or mixtures present. Chemical airborne concentration must be less than IDLH levels. The atmosphere must contain at least 19.5% oxygen.

LEVEL D: Coveralls, safety boots/shoes, safety glasses or chemical splash goggles OPTIONAL: Gloves, escape SCBA, face-shield Protection Provided: No respiratory protection, minimal skin protection. Used When: The atmosphere contains no known hazard. Work functions preclude splashes, immersion, potential for inhalation, or direct contact with hazard chemicals. Limitations: This level should not be worn in the Hot Zone. The atmosphere must contain at least 19.5% oxygen.

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European standards for CPC are based on the type of clothing based on testing of whole garment and are classified as types 1-7, related to the type of exposure of the CPC such as gas-tight, spray-tight, liquid-tight.

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Clothing item service life is an end user decision depending on the costs and risks associated with clothing decontamination and reuse. Protective clothing may be labeled as: Reusable, for multiple wearings; or Disposable, for one-time use. The distinctions between these types of clothing are both vague and complicated. Disposable clothing is generally lightweight and inexpensive. Reusable clothing is often more rugged and costly. The basis of this classification really depends on the costs involved in purchasing, maintaining, and reusing protective clothing. CHEMICAL PROTECTIVE CLOTHING APPLICATIONS 1. Protective clothing must be worn whenever the wearer faces potential hazards arising

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from chemical exposure. Some examples include: Emergency response; Chemical manufacturing and process industries; Hazardous waste site cleanup and disposal; Asbestos removal and other particulate operations; and Agricultural application of pesticides. 2. Within each application, there are several operations which require chemical protective clothing. For example, in emergency response, the following activities dictate chemical protective clothing use: Site Survey: The initial investigation of a hazardous materials incident; these situations are usually characterized by a large degree of uncertainty and mandate the highest levels of protection. Rescue: Entering a hazardous materials area for the purpose of removing an exposure victim; special considerations must be given to how the selected protective clothing may affect the ability of the wearer to carry out rescue and to the contamination of the victim. Spill Mitigation: Entering a hazardous materials area to prevent a potential spill or to reduce the hazards from an existing spill (i.e., applying a chlorine kit on railroad tank car). Protective clothing must accommodate the required tasks without sacrificing adequate protection. Emergency Monitoring: Outfitting personnel in protective clothing for the primary purpose of observing a hazardous materials incident without entry into the spill site. This may be applied to monitoring contract activity for spill cleanup. Decontamination: Applying decontamination procedures to personnel or equipment leaving the site; in general a lower level of protective clothing is used by personnel involved in decontamination. CHEMICAL PROTECTIVE CLOTHING SELECTION FACTORS 1. CLOTHING DESIGN. Manufacturers sell clothing in a variety of styles and configurations. 18 1. Design Considerations. Clothing configuration; Components and options; Sizes; Ease of donning and doffing; Clothing construction; Accommodation of other selected ensemble equipment; Comfort; and Restriction of mobility. 2. MATERIAL CHEMICAL RESISTANCE. Ideally, the chosen material(s) must resist permeation, degradation, and penetration by the respective chemicals. >> Permeation is the process by which a specific chemical diffuses through a material at the molecular level, from the outside to the inside surface of the material. Chemical permeation frequently occurs with no obvious signs of physical degradation of the material. The rate of permeation is affected by factors such as the type of chemical,

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chemical concentration, material thickness, humidity, temperature and pressure. Permeation testing provides two important pieces of data for material selection --- breakthrough time and permeation rate. Breakthrough time is the elapsed time from the initial contact of the chemical on the material exterior to the time of detection of the chemical on the inside surface and is a measure of the time needed for a chemical to soak through the clothing material. The expected duration for handling the chemical must fall well within the breakthrough time of the clothing material under the conditions of use. Permeation rate refers to the rate at which a chemical will move through the clothing material once the chemical has broken through. The higher the permeation rate, the faster the chemical will move through the material. The chemical protective clothing must have a low permeation rate under the conditions of use. >> Degradation involves physical changes in a material as the result of a chemical exposure, use, or ambient conditions (e.g. sunlight). The most common observations of material degradation are discoloration, swelling, loss of physical strength, or deterioration. >> Penetration is the movement of chemicals through zippers, seams, or imperfections in a protective clothing material.

3. PHYSICAL PROPERTIES. As with chemical resistance, manufacturer materials offer wide ranges of physical qualities in terms of strength, resistance to physical hazards, and operation in extreme environmental conditions. Comprehensive manufacturing standards such as the NFPA Standards set specific limits on these material properties, but only for limited applications, i.e. emergency response. 4. EASE OF DECONTAMINATION. The degree of difficulty in decontaminating protective clothing may dictate whether disposable or reusable clothing is used, or a combination of both. 5. COST. Protective clothing end users must endeavor to obtain the broadest protective equipment they can buy with available resources to meet their specific application.

Chemical Protective clothing:

The chemical protective earlier developed used activated carbon as absorbent that absorbs chemicals; the activated carbon granules were coated using polyurethane foam, but this method of coating resulted in heat stress for the wearer due to low air and water vapour permeability of the fabric. In this project we have used activated carbon as the absorbent layer but with a novel method of coating them using needle punching technique. Our chemical protective clothing consists of three layers outer fabric, sorptive layer and inner layer (Refer Fig 2.1).

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The outer shell is a water repellent layer protecting from liquid chemicals, the sorptive layer is the soul of the protective clothing absorbing liquid and air borne chemicals. The inner layer provides comfort to the wearer.

In recent times, carbon has been one of the magnificent elements which have revolutionized materials science. Carbon provides materials with excellent properties for a large spectrum of industrial applications. Carbon exists in different forms from carbon fibres to diamond. Porous carbons can be grouped into two categories: (i) Carbon foams with desired architecture of pores for structural and thermal applications; recently, these have been used as templates for making ceramics, (ii) activated carbons consisting of porous carbons with added active surface chemical groups. Porous carbons, especially activated porous carbons, constitute one of the most important types of industrial carbons and have been in use for thousands of years. Activated carbon in very fine powder or granular form is useful to purify both water and air. Activated carbon has particular affinity to organic materials such as solvents used in printing inks and common coatings.

When the carbon particle becomes saturated with the contaminant, the exit stream will evidence a “breakthrough” of that contaminant, at which time the canister will be replaced and/or reactivated (usually by heat). Since the waste stream usually can’t be interrupted during this regeneration, two or more carbon beds are often designed into the system.

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Activated carbon particles don’t react with most organics, permitting: Recovery through later heat regeneration and separation, or Incineration during regeneration from water-borne streams. Water-born organic streams are usually mixed with activated carbon particles and removed later by filtration. Granular activated carbon is often used in the filter bed itself. It has been used to remove hydrocarbons, oils, phenols, and low concentrations of metals. It isn’t applicable for most heavy metals, nor waste streams with more than 10,000 ppm organics or low molecular weight aliphatic hydrocarbons. Pretreatment of the stream may be advisable where bed clogging by particulates or suspended materials is likely.12

Development of Chemical Protective clothing:

The chemical protective clothing is formed by five layers, the outer shell made of polyester as it has low absorption of 2% and it provides a good strength to the fabric and polyester has a good resistance to lab grade chemicals. The inner layer is made up of cotton fabric as it gives good absorbency and comfort. The middle layer comprises of cotton non woven sandwiched with activated carbon (Refer Fig 3.1).

Also, water/oil repellent finishing is applied on Front Polyester fabric.

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NOVEL TECHNIQUE OF EMBEDING ACTIVATED CARBON Activated carbon is a well known absorbent, there is a world Wide insistence on this product for a multitude of uses, particularly air/gas treatment and Purification, Precious Metal Recovery, in Catalysis and in protective clothing for absorbing of hazardous chemicals. Extensive surface area pores of 5 to 10 A 0 radius, which provides unmatchable adsorption and retentive capabilities for gases and low molecular weight. The activated carbon used in the chemical protective clothing was got from core carbons pvt ltd. The carbon had the following specifications CarbonTetraChlorideAdsorption%---75/85 ApparentDensitygm/cc---0.42-0.47 AshContent(Max)%max---2.5 BallpanHardnessNumber---96.5+ PH---9/11 SurfaceAreasq.M/gm---1300–1400 Size of granules - 0.85 X 0.300 mm

The conventional chemical protective clothing was based on embedding activated carbon using adhesives and polyurethane foam with a activated carbon load of 120 – 160 GSM. These fabrics had low comfort properties of air permeability and thermal comfort causing stress to the wearer. As a solution to this problem selectively permeable membranes were developed. Which is capable of protecting from some chemicals and the membranes are too costly. Another cost effective solution to this problem is the Novel approach of bonding activated carbon using needle punching technology. The novel technique of embedding activated carbon uses a base fabric made of 100 % cotton and needle punched cotton non-woven. The fabric acts as base for the activated carbon and also as a inner lining for the final fabric enabling easy absorption of sweat from the wearer and transporting them to the outer layer. More over the cotton fabric provides comfort to the wearer. The plain woven cotton fabric was spread over the table. Above the fabric needle punched non-woven produced by previously explained technique was placed and the activated carbon particles were spread uniformly over the width and length of the fabric (Refer Fig 3.2). The carbon was spread uniformly to give a GSM of 160. Above the activated carbon layer another layer of needle punched non-woven was placed. The whole assembly was then applied with pressure and wound to form a roll.15

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The activated carbon granules coated over the double pass needle punched fabric gets embedded in the non-woven. The cotton fibres dose not allows the carbon granules to move from its place. The activated carbon coated non woven had a GSM of 341.

Needling: The fabric thus prepared was fed in to the needle punching machine through a pair of conveyors and calender rollers. To provide a initial cohesion to the layers a pressure of 6 bar was maintained at front and back pair of calender rollers. The web was fed such that the cotton woven fabric as the top layer. The fabric layers were needle punched with following settings: Infeedspeed:0.4m/min Drawoffspeed:0.4m/min Strokes/min:152 Depth:15mm Width:700mm The activated carbon granules held in its position by the cotton fibres in the non woven is further locked by needle punching where the fibres from the top and bottom layer are drawn through the fibre web causing the fibres to occupy vertical position. The resulted composite fabric had a good locking of activated carbon granules. The woven cotton fabric was also bonded together. In the final fabric a uniform layer of cotton fibres was seen on the reverse side of the cotton woven fabric. Bonding of nonwoven and polyester fabrics:

The activated carbon sandwiched non woven and polyester fabric are bonded together using acrylic resin. Acrylic resin provides a good strength along with flexibility. The fabric is placed on a platform and the resin is uniformly sprayed on the fabric using a hand spray gun and the cotton non woven is placed over the fabric and the fabric is applied with uniform pressure. Thus prepared fabric is cured at 1100c for 2 min (Refer Fig 3.3 & 3.4).

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EVALUATION OF BARRIER PROPERTIES OF PROTECTIVE CLOTHING The tests for assessing the performance characteristics of chemical protective clothing:16,17 1. Degradation resistance 2. Penetration resistance 3. Permeation resistance Degradation resistance test can only be used as a screening test which can show clear impossibility of using particular material for certain chemicals. Whereas; barrier properties of CPC can be determined by penetration and permeation resistance tests. Degradation resistance Degradation is defined as change in a material�s physical properties as a result of chemical exposure. [physical properties may include weight of material, dimensions, tensile properties, thickness or any other characteristic. Which may influence the performance of protective clothing when used in particular application. Dramatic degradation due to chemical exposure indicates the total incompatibility of the material with the chemical.

Penetration Resistance:

Penetration is defined as the floe of chemicals through closures, porous materials, seams and pinholes or any other imperfection in protective clothing. The penetration resistance tests is divided into two categories viz. Run-off based tests and hydrostatic based tests. Run-off Based tests:

These tests are characterized by contact of liquid chemicals with the materials by force of gravity over a specified distance. Usually specimen is supported at an angle of 45 degree allowing chemical to run-off, a large amount of water is delivered onto the

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specimen and the amount of water underneath the specimen is measured. Index of penetration(P)=Mp/Mt*100 Where: Mp= mass of the liquid deposited under the specimen Mt= mass of test liquid discharged onto the test specimen Hydrostatic based tests:

It involves pressurization liquid behind or underneath the specimen. Water is used as challenge liquid. Water is introduced above the clamped specimen at a pressure controlled by water in rising column. A mirror is fixed below the specimen to allow the operator to view the underside of specimen for appearance of water droplets. The hydraulic pressure is increased until leakage occurs underneath the specimen. Limitations of penetration resistance tests:

1. visual observations involved in the test leads to bias results. 2. liquid penetration in most cases occurs in the form of fine droplets which is difficult to be visualized. 3. water is used as a challenge liquid which has different nature than actual chemical. Permeation resistance Permeation is a process of chemical penetration into chemical protective clothing at molecular level. In this process, chemical is first absorbed on exposure side of material, then diffused through material and finally desorbs from the other surface. Resistance of the material to permeation is expressed in terms of break through time and permeation rate. Break through detection time is defined as the elapsed time measured from the start of the test to the sampling time that immediately proceeds the sampling time at which the test chemical is first detected. Break through time is an important consideration when choosing between CPC materials with similar degradation characteristics, while permeation rate is a measure of flux through a unit area of material for a unit time.

Risks Developing because of usage of Chemical protective clothing:

Heat Stress. Wearing full body chemical protective clothing puts the wearer at considerable risk of developing heat stress. This can result in health effects ranging from transient heat fatigue to serious illness or death. Heat stress is caused by a number of interacting factors, including:17 Environmental conditions; Type of protective ensemble worn The work activity required; and The individual characteristics of the responder. When selecting chemical protective clothing and equipment, each item’s benefit should be carefully evaluated for its potential for increasing the risk of heat stress. For

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example, if a lighter, less insulating suit can be worn without a sacrifice in protection, then it should be. Because the incidence of heat stress depends on a variety of factors, all workers wearing full body chemical protective ensembles should be monitored.

Heart Rate Count the radial pulse during a 30-second period as early as possible in any rest period. If the heart rate exceeds 110 beats per minute at the beginning of the rest period, the next work cycle should be shortened by one-third. Oral Temperature Do not permit an end user to wear protective clothing and engage in work when his or her oral temperature exceeds 100OF (38OC). Use a clinical thermometer (three minutes under the tongue) or similar device to measure oral temperature at the end of the work period (before drinking), as follows: � If the oral temperature exceeds 99.6OF (37. OC), shorten the next work period by at least one-third. � If the oral temperature exceeds 99. OF (37. OC) at the beginning of a response period, shorten the mission time by one-third. Body Water Loss Measure the end user’s weight on a scale accurate to plus or minus 0.25 pounds prior to any response activity. Compare this weight with his or her normal body weight to determine if enough fluids have been consumed to prevent dehydration. Weights should be taken while the end user wears similar clothing, or ideally, in the nude. The body water loss should not exceed 1.5% of the total body weight loss from a response.

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References:

1. A book on Technical Textiles—WoodHouse Publication 2. Grant,T.L.& Crown E.M.(2001) Electrostatic properties of thermal-protective

fabric systems Journal of Textile Institute, 92part1 3. www.gentexcorp.com 4. www.textiles.edu 5. Perkin S.W. Functional Finishes and High performance Textiles, Textile

Chemists and colourists and American dyestuff reporter 32(4) 2000 6. Palacin F Textile Finish Protects against UV Radiation, Melliand International

1997 7. Achwal W.B. UV Protection by textiles Colourage 2000 8. Mallik S.K., Arora T. UV Radiations Problems and remedies Man made

Textiles in India 2003(5) 9. Dayal A, Aggarwal A.K. Textiles and UV Protection Asian Textile Journal

1998(9) 10. Rupp J, Hilden J Textiles for Protection against harmful UV radiation

International Textile Bulletin 2001(6) 11. Holme I. UV absorbers for protection and performance International Dyer

2003(4) 12. Singh M.K. Sun Protective clothing Asian Textile Journal 2005(1-2) 13. Sekar N UV absorbers in Textiles Colourage 2000 14. www.labsphere.com 15. AATCC Review 2005 16. G. Chandramohan, K.P. Chellamani Protective Textiles Texindia fair 2000 17. Bille J Collier Textile Testing and analysis, prentice Hall Inc, USA 2002 18. Handbook of Technical textiles A.C. Horrocks