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1 A Preliminary Look at the Nature, Causes, and Consequences of Plastics Failure

■ 1.1 Introduction

This book is not the fi rst to deal with plastics failure. For example, Failure of Plastics [1] provides detailed reviews of many types of failure, including theoretical aspects. The present work picks up from that point, and concentrates on the practical tech-nological considerations, with many examples of actual failures from the author’s experience and from the literature [2–4]. Plastics failure can cause economic and legal problems, as well as contribute to personal injury or death. Public perception of plastics is adversely aff ected by their failures, such as the bad reputation that early plastics earned with toys that broke too easily. Recently, plastic toys from a non-United States company had high levels of heavy metals that could harm the human body. Figure 1.1 shows a toy with a lead level greater than that allowed by the United States Consumer Product Safety Commission [36]. The lead was in the paint coating.

Failures are usually not expected, and o� en occur abruptly. Service or functioning of a whole system dependent on a small plastic part that fails could be interrupted.

FIGURE 1.1 A plastic toy with high lead content in the paint coating (courtesy of The Madison

Group, Madison, WI, www.madisongroup.com)

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2 1 A Preliminary Look at the Nature, Causes, and Consequences of Plastics Failure

It is a practical necessity to know why plastics fail, so that failures can be mini-mized or eliminated. The diff erence between good performance and long life, and failure, can result from a seemingly small diff erence in the variables that aff ect plastics properties. While it is most o� en thought of as fracture, failure occurs in many other ways (Section 1.9).

Other books about the failure of various polymeric materials have been published since the fi rst edition of Plastics Failure Guide, or were not included in the fi rst edition [5–26]. Papers on plastics failure, plastics analysis, and related subjects by Myer Ezrin and coauthors, are listed in Section 1.14. Abstracts of some Annual Technical Conference (ANTEC) papers since 1999, and of some other SPE (Society of Plastics Engineers) publications, are available free of charge from the SPE website [27]. Full papers are available to SPE members and subscribers to journals. The Failure Analysis and Prevention Special Interest Group of SPE has sessions on failure each year at ANTEC. The papers are published in the Conference Proceedings. Other technical units that may have failure-related papers from time to time are the Plastics Analysis Division, the Engineering Properties and Structure Division, the Medical Plastics Division, and others.

■ 1.2 Plastics

Compared to other materials, such as metals, glass, and stone, plastics have existed for only about 125 years [28, 29]. Other materials go back many hundreds, if not thousands, of years. Large-scale development of plastics is only about 60 years old. The fact that failure of plastics does occur is not surprising, given their short history and the recent evolution of many plastics materials, processes, and applications. The fi rst commercial plastic, nitrocellulose, was patented by John Hyatt [29] in 1869. Failures similar to those of more modern plasticized plastics were caused by factors such as embrittlement due to volatilization of plasticizer, poor thermal stability, and fl ammability. The problem of celluloid movie fi lm catching fi re is well known. John Hyatt used his newly-invented material to coat billiard balls made of pressed wood and bone dust. Unfortunately, the nitrocellulose gave a mild explosion when the billiard balls made aggressive contact. One saloon keeper stated that “every time the balls collided, every man in the room pulled a gun” [37].

The term plastic implies an ability to fl ow or be formed, generally under pressure. Thermoplastic means a material that can be formed with heat, typically also under pressure. A thermoset plastic usually goes through a plastic stage during formation, a� er which it becomes crosslinked and then is no longer thermoplastic (Fig. 2.5). Between these two extremes of plastic types, there is a world of diff erent plastics

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31.3 Polymers

materials, processes, and applications. One of the objectives of this book is to provide an understanding of the fundamental nature of plastics on which to base a sound approach to determine the cause of, and ultimately prevent, plastics failure.

■ 1.3 Polymers

Plastics belong to the generic family of materials called polymers. “Poly” means many, and “mers” refers to basic or individual units of the polymer molecule. For example, polystyrene is the polymer made by polymerizing the monomer styrene. Polymers have a high molecular weight, and long molecules in which a basic unit of composition is repeated many times. It may be compared to a long chain with many links connecting the same unit over and over again. A polymer chain is measured as the sum of the atomic weights of all the atoms present. While the monomer styrene has a molecular weight of about 100, polystyrene has a molecular weight 102–104 times higher (10,000–1,000,000). A polymer may contain as many as 100 to 10,000 monomer units linked together. This high molecular weight, compared to nonpolymeric materials, is the primary feature that sets them apart from other materials, and accounts, to a great extent, for the unusual strength and chemical resistance of polymers. Unfortunately, along with high molecular weight comes high-melt viscosity, or resistance to fl ow, and processing problems. High temperature needed to reduce melt viscosity to manageable levels may contribute to degradation during processing. Thermal degradation lowers the molecular weight, thus aff ecting product properties dependent on high molecular weight. High-melt viscosity also means that polymer molecules that have become aligned or oriented during fl ow in processing are slow to return to a disoriented state. Rapid cooling contributes to inhibiting the return to a normal disoriented relaxed state before the part solidi-fi es. The result is that the plastic part or material has internal stress (Chapter 2), with consequent potential for failure by environmental stress-cracking, warpage, or weak weld lines. A signifi cant percent of plastics failures are due to problems such as poorly fused products, frozen-in stress, and weak weld lines, many of which are due to the problem of processing high molecular weight, viscous material.

Another consideration with polymers is that, in some cases, their composition and structure permit the long polymer molecules to come together in a highly-ordered crystalline state (Chapter 2). While generally desirable and contributing to strength, it can also be a factor in failure, partly because crystalline order can be aff ected by processing conditions and service conditions. The combination of molecular weight and crystallinity can make for a very successful product, or for a miserable failure with unfortunate consequences. To a great extent, plastics product designers and

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engineers have to be “molecular engineers.” Like a detective looking for clues to solve a mystery, the plastics failure analyst has to consider the subtleties, namely the clues that may or may not be important; the sequence of events from the manufacture of the plastic material, its transportation, storage, compounding, testing, conditioning prior to processing, processing, conditioning a� er processing, QC testing, service conditions, product design, mold design, condition of the processing equipment, joining and welding conditions, and ultimately, the in-service use and environment.

■ 1.4 Rubbers and Elastomers

These materials are also polymers, and bear a close resemblance to plastics. Usually, elastomer refers to the polymer used to make rubber. In general, rubber is fl exible at room temperature (glass transition temperature less than 25 °C), while most plastics are tough and rigid at room temperature (glass transition temperature greater than 25 °C). All the same considerations of material, design, processing, and end use conditions apply to their failure as they do to plastics.

■ 1.5 Natural Polymers

Most plastics are synthetic polymers made with monomers such as styrene, ethyl-ene, and vinylchloride. But there is a large category of polymers that have existed naturally, long before we started making synthetic polymers. Examples of natural polymers are proteins (polyamides from amino acids) and cellulose (the polymer of glucose). The latter polymer is the primary one responsible for paper and wood products. Natural polymers such as these constitute the main building blocks of animal and plant life (Chapter 15, Failure of Human Biopolymers). As with syn-thetic polymers, high molecular weight is a fundamental feature, together with intermolecular order (crystallinity). When a twig or branch falls from a tree and becomes brittle with time, it is due to one or more of a number of changes, includ-ing breakdown in molecular weight and structure, and loss of water, which acts as a plasticizer. This is analogous to a plastic part becoming brittle and failing as a result of exposure to heat and light, causing breakdown of the polymer. With nylon, simply drying out can signifi cantly embrittle it, as a result of losing the plasticizing action of water. Another example of how natural and synthetic polymers respond in similar ways to common forces is what happens when we wash our hands too o� en, or with harsh soaps or detergents. Chapped and cracked hands o� en result,

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51.6 Plastics in the Family of Materials

due to the removal of body oils that normally so� en the skin and prevent cracking. With plasticized PVC, service conditions can remove some plasticizer, resulting in a brittle fi lm likely to crack.

■ 1.6 Plastics in the Family of Materials

Some of the other materials that plastics supplement or compete with are metals, ceramics, glass, and concrete. In spite of their ease of breakage, glass containers and windows are used extensively. Unbreakable windows are made of polycarbonate, but they tend to scratch easily. This can be reduced by a scratch-resistant coating. Many metal products corrode or rust in service. While plastics are not completely free of problems, corrosion does not occur as it does for metal. These examples illustrate how plastics supplement or improve on the properties of competitive materials such as metal and glass. Plastics have made major inroads in replacing products made of metal, wood, and glass. Since 1979, the global volume production of plastic has surpassed steel [38]. More than half of all containers are made of plastic, replacing glass. Many paper and cardboard packages and bags are now made of plastic. Plastics have replaced many metals. A major part of the weight reduction and attendant fuel saving of automobiles is due to the replacement of many metal parts by plastics, saving weight of the order of 400 to 500 lbs per automobile. In food wrapping, thin fi lm plastics compete with aluminum foil. Plastic and wood are mixed together and extruded into planks for replacement of wood decking. This decking does not require yearly treatments to prevent rotting or attack by insects.

■ 1.7 Common Features and Diff erences in Performance or Failure of all Materials

Using metals for illustration, the same basic considerations apply to the manufac-ture of metal products and to plastics products. Four major areas to consider are:

1. Material—the polymer or polymers, plus all additives and contaminants

2. Design—dimensions, reinforcements, stress sites

3. Processing—thermal and orientation eff ects, degradation during processing, uniform dispersion of materials

4. Service conditions—heat, humidity, outdoor exposure, chemical resistance, fatigue

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User15%

Material45%

Processing20%

Design20%

FIGURE 1.2 Cause of failures by percent [38] (adapted from Rapra

Technology, Ltd, UK)

The fi rst three are chosen to satisfy the service requirements. Failure is the result of inadequacy in material, design, processing, or end use. There is o� en consider-able interaction of the four factors. One design may tolerate greater variation in material characteristics, such as molecular weight, than another design. If suffi cient design reinforcements are used, and areas of stress concentration are minimized, the part performance may not depend so much on material properties. A study of 5000 failures was conducted by David Wright [38], who classifi ed the failures into the four factors listed above and in Figure 1.2.

As this pie graph illustrates, 85% of failures are related to the manufacture of the part: design, material, and/or processing. In a sense, the part was faulty prior to leaving the factory. An engineer, at some point during manufacturing of the part, could have prevented failures of the part from occurring. In Wright’s study, some failures caused by abuse or accidents are more than likely unrepresented, since they may have been obvious and did not make it into the study. Thus, the 15% of failure related to user abuse may be an underestimate. Nevertheless, the number of failures not associated with abuse is extremely high.

Service conditions are unpredictable, and may be underestimated. Furthermore, the simultaneous application of two conditions may cause failure in a way, and in a time frame, that would not likely occur under the infl uence of each alone. A common example is environmental stress-cracking, to which polyethylene is particularly prone. A chemical alone, not under stress, or stress in the absence of chemical agent, is much less likely to cause failure than when the two conditions are applied together. One of the subtle aspects of failure analysis is that stress suffi cient to interact with environmental stress-cracking agents to cause failure may be present within the part as a result of processing. To a great extent, such internal stress is unavoidable. The trick is to introduce as little frozen-in stress as possible into a satisfactory, economical part, such that it will not fail within its expected service life. To show the diversity of plastics applications and what constitutes failure, shrink tubing is designed to shrink with the application of heat. If processed improperly, so that

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71.7 Common Features and Diff erences in Performance or Failure of all Materials

the degree of orientation is lower than needed to achieve the required shrinkage, that product will have failed for a reason that most other plastics processors work very hard to have in their products: a low level of frozen-in stress.

As an example of underestimated service conditions in regions with acidic precipita-tion commonly known as “acid rain,” some plastics and other materials in outdoor applications may have their life shortened due to chemical or physical eff ects of acid. The problem may stem, in part or whole, from the eff ect on a component or reinforcing agent, such as glass fi ber, under stress in the application [30].

As for the materials aspect, polymers and plastics involve choices of molecular weight, chemical composition, and intermolecular order (crystallinity, degree of orientation, degree of fusion). For metals, molecular weight is not a major consid-eration as it is with plastics, but composition and intermolecular order are. The molecular weight of metals is the molecular weight of the elements themselves, of the order of 50 to 100. When metals are processed, they have to be heated high enough to melt the crystalline structure; but then the viscosity is very low, and they can be poured very easily. High pressure is not a requirement in the processing of metals as it is with most plastics.

Many of the same types of failure apply to metal products as to plastics, including fatigue, brittle fracture, thermal expansion and contraction, corrosion, or other damage due to water and other chemicals (environmental eff ects). In both cases, design must take into account those features that may contribute to failure, such as stress raisers like notches and holes. Fundamental considerations in design of metal products and plastics products are alike to a signifi cant extent. A paper [31] on corrosion of metal water tubes in a nuclear reactor reads remarkably like a paper on plastics environmental stress-cracking might. For example, stress corrosion cracking requires the coincidence of three factors: susceptible material, aggressive environment, and stress.

It cannot be emphasized too much that the unique, distinctive feature of plastics and all polymers that make them diff erent from other materials is their high molecular weight, or long chain nature. It aff ects the processing of plastics in a unique way, and is a primary factor in contributing to the performance, or failure, of plastic products. Plastics derive their desirable features of strength and chemical resis-tance, in large part, from their high molecular weight. Control of molecular weight in selection of the starting material, and not allowing it to be reduced signifi cantly in processing, are absolutely essential to plastic products. The plastics engineer has a great challenge to produce useful products of long life, in spite of the diffi cult requirements of plastics processing that result from wrestling huge molecules that may have molecular weights as high as 100,000 to 1,000,000. Annealing a� er manufacture may be needed to reduce internal stress, to ensure that the product won’t fail in service. Annealing is important in some metal products, to ensure that

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the products have the desired crystalline structure and freedom from internal stress required for the application. Annealing is also a standard feature of glass blowing.

■ 1.8 Unintentional Factors Aff ecting Failure

Some of the factors that aff ect performance or failure are “intentional,” or at least expected, while others are “unintentional.” For the material, some substances present are not there by choice, and their presence may not be known or realized. Examples are water, compounding process aids, and contaminants from resin manufacture, packing, or transportation. In processing, frozen-in stress is usually unintentional. A plastic that continues to crystallize in service, resulting in shrinkage or other undesirable eff ects, is undergoing unintentional or delayed processing. Service condi-tions may cause failure due to conditions that are too severe, or were not anticipated at all. A common example is environmental stress-cracking, in which a devastating eff ect results from simultaneous application of stress and environmental agents. An important part of plastics failure analysis is to discover the unintentional factors, and to assess their contribution to failure. An example of “too severe service condi-tions” is given in the race car accident in Section 1.9.1.

■ 1.9 Types and Causes of Failure

Failure is any malfunction or deviation from the norm that signifi cantly detracts from performance. Excessive plastic deformation, or shrinkage, wear, or loss of attractive appearance may constitute failure just as much as fracture does. At times, several diff erent modes may combine to produce the resultant failure. Some of the failure types and causes are given in Table 1.1.

Failure in one case may be the intended result in another. For example, if a plastic is supposed to tear or break easily to permit entry into a bottle or package, but resists breakage or tearing, then that is a failure—the failure to behave as intended. High orientation or frozen-in stress is usually undesirable in most products, causing shrinkage, distortion, and cracking to relieve the stress. While high orientation is required for some applications, such as fi bers or “living hinges” (Fig. 4.55), many plastics are designed for one-time, disposable service. If they break when someone makes multiple or improper use of them, that should not be considered failure in the usual sense. At the other end of the service life spectrum are applications requiring life of many years. Electrical power distribution cables, for example,

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91.9 Types and Causes of Failure

are expected to be in service for 40 years or more without failing. Electrical or mechanical breakdown in 20 years would constitute a failure. At 45 years, 5 years beyond expected service life, it would not be fair to call that failure, just as failure of a one-time, usually disposable product being used a� er its intended service is not really a failure. Failure should be judged in the light of the product design and expected service life.

One of the most diffi cult things to do is to estimate service life accurately. One can minimize chances of early failure by a substantial safety factor in design and/or material, but that adds cost. Estimated life is usually based on accelerated service conditions. Many factors may aff ect the reliability of the procedure, such as the choice of tests performed, and whether the polymer changes in the same way under accelerated conditions as during normal service. For example, if a diff erent mechanism applies as a function of temperature, extrapolation of test results to a lower temperature may not be realistic. Nevertheless, the procedure has worked well in setting temperature ratings of plastics by Underwriters Laboratories [32]. Another is plastic pipe testing, using procedures of the Plastics Pipe Institute [33].

Service life depends on the severity of service conditions. Any service life estimate is based on certain assumed service conditions. If these are signifi cantly more severe, failure in a shorter time may occur. Failure is a very complex matter that may be fully within normal expectation, or may be unexpected, depending on material, design, processing, and service conditions.

In Table 1.1, Item 14, a new type of failure has been added: failure to be allowed to be sold, i.e., banned, by legislation or regulation by a governing body, usually for health reasons. Similar action of non-governmental bodies, such as a major corporation like Walmart, may have the same eff ect as being banned legally. PVC plasticized with phthalate plasticizers has been banned in products for babies under three years old by San Francisco, California, and by the State of California, as well as other states and countries. Polycarbonate (PC) and food contact epoxy resin coatings are under fi re for their monomer, bisphenol A (BPA). The San Francisco ban of PVC with phthalates includes a ban on BPA-containing products for babies under three years old (Chapter 16, Environmental, Recycling, and Health Aspects of Plastics Failure).

As a simple example of the eff ect of design on failure of all materials, part dimen-sions suitable for the application must be adequate. A soap bar breaks when it becomes thin from use. The same bar will not fracture in use when it is new or has not lost too much of its original thickness. The principle of adequate thick-ness for the application applies to all materials and designs, bearing in mind the characteristics and limitations of the material. Reinforcing ribs and freedom from unnecessary areas of high stress, for example, apply generally to products of most materials.

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TABLE 1.1 Some Types and Causes of Failure

1. Fracture1.1 Due to product as made, not due to degradation from aging1.2 Due to degradation from aging (thermal, ultraviolet and visible light, ozone, rain, nuclear

radiation). May be caused by inadequate stabilizer/antioxidant content, or their loss by migration, extraction, or evaporation

1.3 Embrittlement due to loss of plasticizer or water in service1.4 Fracture due to too much regrind of low molecular weight

2. Creep2.1 Material undercured or heat resistance too low for service conditions2.2 Stress applied for long periods of time, resulting in unacceptable deformation

3. Crazing and stress-cracking3.1 Fracture or crazing due to an internal environmental chemical or stress-cracking agent3.2 Fracture or crazing due to an external chemical or stress-cracking agent3.3 May occur due to high level of internal stress or to externally applied stress

4. Fatigue4.1 Fracture due to repeated application of tensile, fl exural, or shear stress, such as opening

and closing of a hinged part, or repeated impact leading to crack formation and growth

5. Low adhesive bond strength for applications requiring high bond strength5.1 Thermally bonded heat seals5.2 Seals made with an adhesive

6. High adhesive bond strength for applications requiring low bond strength6.1 Thermally bonded heat seals6.2 Seals made with an adhesive

7. Co-extruded fi lm adhesion failure7.1 Low bond strength due to interfering substances at the interface

8. Warpage or distortion8.1 As made, due to processing conditions8.2 Severe service conditions8.3 Partial inward distortion of containers holding liquid products

9. Shrinkage9.1 Too-high temperature in service may cause release of orientation.

Possible especially for parts made with residual frozen-in stress

10. Change in appearance10.1 Color change or fading

Improper choice of dye or pigment Migration of dye Degradation on aging Discoloration due to processing at high temperature with fl ame retardants in the compound Discoloration due to processing of polymers sensitive to temperature

10.2 Change in surface gloss10.3 Change in transparency—development of haze or cloudiness

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111.9 Types and Causes of Failure

11. Toxicity and odor11.1 Odor due to residual solvent or monomer

11.2 Migration of toxic substance, e.g., monomer or solvent, into food or other product in excess of regulations

12. Failure caused in a contiguous material by migration of an additive from or into the plastic product

12.1 Color transfer

12.2 Antioxidant/stabilizer transfer resulting in accelerated degradation

12.3 Plasticizer migration into adhesive layer on fl ooring causing loss of adhesion

13. Power distribution (electrical cable failure (5–35 kV)13.1 Water treeing—combined eff ect of water and electrical stress

14. Failure to be allowed to be sold, i.e., banned, by legislation or regulation of a legis-lative body, usually for health reasons

Failure may be the result of poor processing conditions that can be detected before the product is sold. Quality control should be able to catch potential product fail-ures resulting from processing before they reach the customer. One of the reasons plastics are so attractive and economical is that they can be produced rapidly and eff ectively by methods like injection molding, blow molding, and extrusion. But these processes result in a high level of orientation, a frequent contributor to failure. Many failures are predictable, provided that the correlation between the basic features of the product and properties are known.

Failure of plastics packaging to degrade or become harmless when discarded into the environment a� er use is a major cause of public criticism. For example, most common plastics used for packaging fl oat in water, due to low density. Unfortunately, plastics discarded in the oceans do not degrade, for all practical purposes. Marine animals have died from eating indigestible plastics, and from being fatally trapped by plastics picked up on beaks or noses (Fig. 16.6). While it may seem unrealistic to consider such cases as plastics failure, anything that detracts from the acceptability of plastics products is a failure. Certainly any condition that threatens to prohibit the use of plastics in a major application area is a failure of enormous magnitude, and threatens to make all other types of failure irrelevant and obsolete (Chapter 16, Environmental, Recycling, and Health Aspects of Plastics Failure).

1.9.1 When Failure is Not Really a Failure

Failure of plastic parts o� en occur that are not a failure in the traditional sense. Some failures are expected, save lives, and prevent other failure from occurring.

TABLE 1.1 Some Types and Causes of Failure (continued)

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For example, the race car shown in Figure 1.3 crashing into the wall demonstrates plastic’s ability to absorb energy and dissipate it away from a certain area or object, in this case the driver. Though the plastic body panels fractured into many pieces, as seen fl ying off in the fi gure, the driver more than likely did not think the plastic failed. He lived through this crash, though his legs are visible dangling from the car as it went airborne from impact. If the plastic car body had collapsed without fracture, the driver might have been crushed and possibly killed, depending on whether or not there were airbags, and how well they would have worked [40].

Other plastic parts are designed to fail, to prevent tampering or overtightening. Figure 1.4 shows a cap to a beverage bottle that will break when twisted off [40]. The design and material properties of the plastic cap are critical to ensure that it does not take too much eff ort to fail, or the consumer may not be able to get the contents out. The wings of the plastic nut shown in Figure 1.5 are specifi cially designed to break off if too much torque is applied. At a high torque, damage to other components that are in contact with the nut are likely to occur. Failure of the wings on the nut prevent this failure from taking place.

FIGURE 1.3 Plastic body panel of a race car as it crashes at the Indianapolis 500 raceway

in the USA. The driver’s legs protrude from the fractured front of the race car (arrow)

(adapted from Sports Illustrated website, May 26, 2005)

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131.10 The People Factor

FIGURE 1.4 Breakage of the beverage cap indicates this container has been tampered with

(courtesy of The Madison Group, Madison, WI, www.madisongroup.com)

FIGURE 1.5 Wings on this plastic nut are designed to break at a high torque

(courtesy of The Madison Group, Madison, WI, www.madisongroup.com)

■ 1.10 The People Factor

People involved in one phase or another of the manufacture of plastics products may contribute to their failure, whether they realize it or not. The people involved include the designer, the person who selected the plastics to use, the plastics sup-plier, the plastics compounder, the processor or supervisor, the machine operator, the QC supervisor, the QC operator or technician, and the salesman who sold the product on the basis of certain performance capabilities. Any one of these can cause

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or contribute to failure. A major consideration in preventing failure is that people must understand that what they do can make the diff erence between success and failure; and that sometimes, they must communicate with others in the chain, in a persuasive, diplomatic way. This o� en includes the processor and designer. The salesman must not oversell the product, leading to unrealistic expectations for its performance. Some of the people in the chain may have little or no technical background, let alone an understanding of polymer science and technology. To compensate for this, a person with overall responsibility for the manufacture of the product should ideally have suffi cient knowledge and understanding of plastics, plastics processes, and product evaluation, to know when a problem may develop, and to prevent an expensive legal case against the company.

■ 1.11 The Consequences of Plastics Failure

The reputation of plastics has been severely damaged by well known failures, such as early toys that broke due to the inherent brittleness of polystyrene. Many such failures were eliminated by rubber modifi cation of the polymer to give impact-grade polystyrene and ABS (acrylonitrile-butadiene-styrene). But the impression of plas-tics as being unreliable lasted a long time. More recently, plastics have become so ubiquitous, and somewhat less likely to fail, that the public’s perception of plastics has improved from the days of the early polystyrene toys. There is still, however, a great deal of room for further improvement.

The very nature of failure is that of an unexpected malfunction, or an unanticipated failure to perform. Some cases, such as fractures, may lead to abrupt changes in the normal functioning of entire systems. A $20,000 automobile, for example, may be le� inoperable because of the fracture of a $1.00 plastic part. If the part failure causes loss of control of the vehicle, the damage to the car may be extensive and, more importantly, the occupants and/or others in the path of the car may be injured or killed. Failure of plastics, or of any other material, is a serious matter.

In Chapter 14, Adhesion Failure of Plastics (Section 14.4.1.1.1), a fatal accident due to the failure of epoxy adhesive to prevent loosening of ceiling bolts is reported (Section 1.14 [41]). This led to the collapse of a suspended concrete ceiling, killing a passenger in a car driving through the tunnel. An inappropriate epoxy had been used that could not withstand the heavy load, causing creep and bolt loosening. Another adhesive was available from the same supplier that would not have failed.

In Chapter 6, Section 6.3.1.3, a motorcyclist was severely injured when polycarbon-ate brake levers broke due to environmental stress-cracking, and the motorcycle could not be stopped.

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151.12 Legal and Financial Aspects of Plastics Failure

■ 1.12 Legal and Financial Aspects of Plastics Failure (see Chapter 9) [3, 34]

Companies can be put out of business because of one serious failure, especially if loss of life or serious injury is involved. The cause of a failure may be due to improper resin received from the supplier, improper compounding by a compounder to introduce additives by way of a concentrate, poor processing, or service condi-tions beyond what was intended for the product. If a sample of the original resin and of the concentrate used to make the failed product were retained, it might be possible to determine if the failure started with the resin or the processing, or if perhaps the concentrate were involved. If the resin were not available, it might not be possible to ascribe the fault to the resin supplier or the processor. Continuous processing, in which new batches of resin are placed in the top of a silo feeding the processing machines, makes it hard to pin down the particular lot of resin used in making a certain group of products.

A failure may also be due to poor design of the product. This too may be diffi cult to prove. In any case, the essence of accountability of the cause of failure requires documentation of every stage of the process, from design to material to processing to quality control. The resin used must be shown to have acceptable properties in accordance with specifi cations. Process conditions must be shown to have been normal and under control. Regrind use should be shown to have been within normal practice, with control of the acceptability of the regrind for addition to virgin resin. The design records should include testing to show that the products will have adequate safety factors for the applications.

A major plastic resin supplier was sued by a manufacturer of radio cabinets who had gone bankrupt. The claim was that the resin supplier had furnished variable and poor quality resin. In its defense, the supplier submitted quality control records to show they had supplied consistent and good quality material. The QC records were not fully documented in a few places. The court would not allow any of the QC records to be used, and the resin supplier lost the case.

Frequently, a plaintiff will sue all parties concerned in failure litigations, including resin suppliers, designer, consultants, and the processor. If only the processor is sued, the processor may in turn sue the resin supplier or designer. If a processor is a small company with little chance of paying what a court decides against it, the much larger resin supplier may also be sued on the assumption that they will be able to pay. In any case, failure can sweep in all parties, even those remotely involved in the manufacture of the defective product. At all levels of involvement in the product, all people and companies must be prepared to defend themselves. This means that appropriate records must be properly kept, relevant to the product

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or service made or performed. A major concern of companies when they lose legal cases is that their liability insurance premiums may be raised, then raised again if there is another decision against them.

Recalls may sometimes be necessary. A polycarbonate molded part in a baby stroller was prone to fracture, potentially allowing the stroller to roll unexpectedly. Fortunately, there were no serious injuries, and the company carried out the recall in a satisfactory manner. Had there been a serious injury or death of a child, the resolution of the problem might have had quite a diff erent result. The redesign of the part, and greater attention to processing conditions, prevented reoccurrence.

Automotive gasoline tanks in the 2002 Dodge Grand Caravan started leaking a� er the vehicle was purchased and used for a while. Fires resulting in the complete loss of the vehicle were reported. The gasoline tank was blow molded out of multilayered plastic. The leakage occurred where the control valve was hot-plate welded to the tank (Fig. 1.6). The failure was the result of poor manufacturing at the plastic weld. Due to the potentially hazardous conditions and possible loss of life, a recall was ordered by the National Highway Traffi c Safety Administration, and all gasoline tanks of this model minivan (approximately up to 116,000) that were produced during a specifi c period of time in 2001 and 2002 were removed and replaced [39].

Plastics failure can lead to litigation that can bankrupt a company, and possibly even bring charges against individuals.

In the fatal accident involving epoxy adhesive referred to in Section 1.12, the adhe-sive supplier was charged with involuntary manslaughter [35].

CONTROLVALVE

FUEL FILLERHOSE

ROLLOVERVALVE

FUEL PUMPMODULE

FUELFILTER

GROUNDSTRAP

INSPECT THE WELD BEAD

AROUND THEFRONT ROLLOVER

VALVEFRONT

FIGURE 1.6 Schematic of the 2002 Dodge Grand Caravan gasoline tank; the faulty weld

was at the control valve to the tank [39] (courtesy of the United States Highway Safety

Administration)

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171.13 References

1.12.1 Lessons

1. Types and Causes of Plastics Failure1.1 Fracture is the best known type of failure, but there are many others; examples

are fatigue, crazing, creep, shrinkage, warpage, and change in appearance.

1.2 A recent new failure is not to be allowed to make and sell your product; usual cause is for health reasons. It may involve legal banning or by banning by consensus of private companies.

2. Four factors that determine if a product fails or succeeds are given below; they apply to other materials as well, not only to plastics.

1. Material

2. Design

3. Processing

4. Service conditions

3. The most distinctive feature of plastics is their high molecular weight, as well as long chain structure.

4. Failure may entail litigation and a possible high cost for product liability. The end result may be bankruptcy.

■ 1.13 References

The references cited above are from this section of references (1.13).1. Brostow, W., Corneliussen, R. D., Failure of Plastics (1986) Hanser Publishers, Munich2. Plastics Design Forum Advanstar Communications, Cleveland, OH (no longer published)3. Himmelfarb, D., A Guide to Product Failures and Accidents (1985) Technomic, Lancaster,

PA4. Morton-Jones, D. H., Ellis, J. W., Polymer Products—Design, Materials and Processing

(1986) Chapman and Hall, New York, NY5. Engel, L., Klingele, H., Ehrenstein, G., Schaper, H., An Atlas of Polymer Damage

(1981) Carl Hanser/Wolfe Publ. Ltd., London6. Schnabel, W., Polymer Degradation: Principles and Practical Applications (1985)

Hanser Publishers, Munich7. Plastics Design Library Staff Eff ect of UV Light and Weather on Plastics and Elastomers

(1994) William Andrew Publishing, Norwich, NY8. Plastics Design Library Staff Eff ect of Sterilization Methods on Plastics and Elastomers

(1994) William Andrew Publishing, Norwich, NY9. Plastics Design Library Staff Fatigue and Tribological Properties of Plastics and

Elasto mers (1995) William Andrew Publishing, Norwich, NY

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10. Wright, D. C., Environmental Stress Cracking of Plastics (1996) Rapra Technology Ltd., UK

11. Portnoy, R. C. (Ed.) Medical Plastics: Degradation Resistance and Failure Analysis (1998) Plastics Design Library, Norwich, NY

12. Lewis, P. R., Polymer Product Failure (1999) The Open University, UK13. Wypych, G., Weathering of Plastics: Testing to Mirror Real Life Performance (1999)

William Andrew Publishing, Norwich, NY14. Scheirs, J., Compositional and Failure Analysis of Polymers: A Practical Approach (2000)

Wiley, UK15. Moore, D. R., Pavan, A., Williams, J. G. (Eds.) Fracture Mechanics Testing Methods for

Polymers, Adhesives and Composites (2001) Elsevier, UK16. Moalli, J. (Ed.) Plastics Failure Analysis and Prevention (2001) Plastics Design Library,

Norwich, NY17. Wright, D. C., Failure of Plastics and Rubber Products: Causes, Eff ects and Case

Studies Involving Degradation (2001) Rapra Technology Ltd., UK18. Wright, D. C., Failure of Plastics and Rubber Products (2001) William Andrew Publish-

ing, Norwich, NY19. Ryntz, R. A. (Ed.) Plastics and Coatings: Durability, Stabilization and Testing (2001)

Hanser Publishers, Munich20. Weldon, D. G., Failure Analysis of Paints and Coatings (2002) Wiley, UK21. Wypych, G., Handbook of Material Weathering (2002) William Andrew Publishing,

Norwich, NY22. ASM Staff Characterization and Failure Analysis of Plastics (2003) ASM (American

Society for Materials)23. Lewis, P. R., Reynolds, K., Gagg, C., Forensic Materials Engineering: Case Studies

(2004) CRC Press, Boca Raton, FL24. Moore, D. R. (Ed.) The Application of Fracture Mechanics to Polymers, Adhesives and

Composites (2004) Elsevier, UK25. Farshad, M., Plastic Pipe Systems: Failure Investigation and Diagnosis (2006) Elsevier,

UK26. Shah, V., Handbook of Plastics Testing and Failure Analysis (2007) Wiley, UK27. Society of Plastics Engineers, www.4spe.org, Newtown, CT28. Craver, J. K., Tess, R. W., Applied Polymer Science Chapter 48, Organic Coatings and

Plastics Chem., Am. Chem. Soc. (1975) p. 721, Washington, DC29. Trucks, H. E., Designing for Economical Production 2nd ed., Chapter 11, Soc. Of

Manufacturing Engineers (1987) p. 259, Dearborn, MI30. Ezrin, M., Groeger, J. H., Jr. Examination of Field Failures of Fiberglass Rod Guy

Strain Insulators Soc. Plastics Eng. ANTEC Conf. Proc. (1989) p. 160331. McIlree, A., Primary Water Stress Corrosion Cracking Remedies EPRI Journal,

September (1987) p. 5132. Underwriters Laboratories, www.underwriterslaboratories.com, New York, NY33. Plastic Pipe Institute, a Division of the Society of the Plastics Industry, Washington,

DC34. Witherell, C. E., How to Avoid Products Liability Lawsuits and Damages—Practical

Guidelines for Engineers and Manufacturers (1985) Park Ridge, NJ35. Springfi eld, Big Dig Company Denies Guilt Massachusetts Republican Associated

Press, September 6 (2007) p. B636. United States Consumer Product Safety Commission, www.cpsc.gov

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191.14 Papers by Myer Ezrin and Coauthors on Plastics Failure Analysis, Plastics Analysis

37. Fenichell, S., Plastic: The Making of a Synthetic Century, Harper Business (1996)38. Wright, D., Failure of plastics and rubber products: causes, eff ects and case studies

involving Degradation (2001) Rapra Technology Limited, UK, Figure 1-2. Page 6. Figure 1.2 of this book (Ezrin) is similar, but not identical to, Figure 1-2 of Wright

39. United States Highway Safety Administration, Control Valve Recall 2002, Campaign ID-02V274000

40. Gramann, Paul, The Madison Group, Madison, WI, www.madisongroup.com

■ 1.14 Papers by Myer Ezrin and Coauthors on Plastics Failure Analysis, Plastics Analysis , and Related Subjects

Some papers on plastics failure analysis deal with plastics analysis and vice versa. Examples are References 8 and 9.

1.14.1 Plastics Failure Analysis

1. Ezrin, M., Harten, J., Thermogravimetric analysis screening of fl ame retardant thermo-plastics for molding safety Soc. Plast. Eng. ANTEC (1981) pp. 188–189, Boston, MA

2. Ezrin, M., Gartner, J., Test method for evaluation of the resistance of fi berglass rods to combined mechanical and chemical stress IEEE Transactions on Power Apparatus and Systems (1984) Vol. PAS–103, No. 9, pp. 2741–2745

3. Ezrin, M., Materials factors in plastics failure Soc. Plast. Eng. ANTEC (1988) pp. 1492–1494, Atlanta, GA

4. Ezrin, M., Groeger, J. H., Jr. Examination of fi eld failures of fi berglass rod guy strain insulators Soc. Plast. Eng. ANTEC (1989) pp. 1603–1606, New York, NY

5. Ezrin, M., Gallery of Goofs -#20 Plastics Design Forum Sept/Oct (1989) pp. 53–566. Ezrin, M., Case studies of low cost PE, PS and PVC products Soc. Plast. Eng. ANTEC

(1990) pp. 1478–1482, Dallas, TX7. Ezrin, M., Case studies of failures due to unintentional service conditions Soc. Plast.

Eng. ANTEC (1991) pp. 2213–2216, Montreal8. Ezrin, M., Lavigne, G., Failure analysis using gas chromatography/mass spectros-

copy Soc. Plast. Eng. ANTEC (1991) pp. 2230–2233, Montreal9. Ezrin, M., Lavigne, G., Application of direct dynamic headspace GC/MS to plastics

compositional and failure analysis Soc. Plast. Eng. ANTEC (1992) pp. 1717–1719, Detroit, MI

10. Ezrin, M., Gallery of Goofs -#23 Plastics Design Forum (1992) September/October, pp. 29–32

11. Ezrin, M., Lavigne, G., Failures caused by additives and contaminants during process-ing and storage Soc. Plast. Eng. ANTEC (1994) pp. 3302–3305, San Francisco, CA

12. Ezrin, M., Lavigne, G., Case studies of adhesive failure of bonded plastics Soc. Plast. Eng. ANTEC (1995) pp. 3936–3940, Boston, MA

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13. Ezrin, M., Lavigne, G., Klemchuk., P., Holley, W., Agro, S., Galica, J., Thomas, L., Yorgensen, R., Discoloration of EVA encapsulant in photovoltaic cells Soc. Plast. Eng. ANTEC (1995) pp. 3957–3960, Boston, MA

14. Ezrin, M., Lavigne, G., Klemchuk, P., Pickering, J., Holley, W., Galica, J., Agro, S., Nelson, W., Wu, Q., Further studies of discoloration of EVA encapsulant in photo-voltaic modules Soc. Plast. Eng. ANTEC (1996) pp. 3260–3264, Indianapolis, IN

15. Ezrin, M., Lavigne, G., Safety-related failure of polyethylene products Soc. Plast. Eng. ANTEC (1996) pp. 3272–3274, Indianapolis, IN

16. Ezrin, M., Plastics Failure Guide—Cause and Prevention (1996) Hanser Publishers, Munich

17. Ezrin, M., Ref. 2, Section 1.13, Design Watch contributing editor, bimonthly series February (1996)–November (1997)

18. Reference 17, The many causes and faces of plastics failure Feb (1996) pp. 27–2819. Reference 17, Unraveling the ‘mystery’ behind part failure April (1996) pp. 31–3220. Reference 17, Those mischievous molecular monsters June (1996) pp. 23–2421. Reference 17, The high cost of part failure Aug (1996) pp. 25–2622. Reference 17, When 1 + 1 = 10 Oct (1996) pp. 29–3023. Reference 17, The three amigos of part failure, success Dec (1996) pp. 25–2624. Reference 17, Plastics failure/people failure Feb (1997) p. 1725. Reference 17, Some eff ects of design in part failure April (1997) pp. 19–2026. Reference 17, Processing can be major contributor to part failure Sept (1997) p. 1627. Reference 17, Processing—or how to torture a polymer molecule, Nov (1997)28. Klemchuk, P., Ezrin, M., Lavigne, G., Holley, W., Galica, J., Agro, S., Investigation

of the degradation and stabilization of EVA-based encapsulant in fi eld-aged solar energy modules, Polymer Degradation and Stability (1997) 55, pp. 347–365

29. Ezrin, M., Processing—Key to preventing plastic part failure Medical Design and Manufacturing Conference, November 6 (1997) Section 304, Minneapolis, MN

30. Ezrin, M., Lavigne, G., Helwig, J., Product failure due to design, material and processing problems Soc. Plast. Eng. ANTEC (1998) pp. 3147–3150, Atlanta, GA

31. Ezrin, M., Lavigne, G., Case studies of failure related to improper formulation Soc. Plast. Eng. ANTEC (1999) pp. 3346–3349, New York, NY

32. Ezrin, M., Zepke, A., Helwig, J., Lavigne, G., Dudley, M., Plastics failure due to oxidative degradation in processing and service Soc. Plast. Eng. ANTEC (2000) pp. 3108–3112, Orlando, FL

33. Ezrin, M., The role of fundamentals, visual observation and state-of-the-art instru-mental methods in solving plastics failures Soc. Plast. Eng. ANTEC May (2002) pp. 3062–3066, San Francisco, CA

34. Ezrin, M., Lavigne, G., Failures due to compositional factors Soc. Plast. Eng. ANTEC May (2003) pp. 2927–2929, Nashville, TN

35. Ezrin, M., Lavigne, G., Gas chromatography/mass spectroscopy for plastics failure analysis Soc. Plast. Eng. ANTEC May (2004) pp. 3000–3004, Chicago, IL

36. Ezrin, M., Lavigne, G., Gas chromatography/mass spectroscopy for plastics failure analysis First Int’l Conf. on Engineering Failure Analysis, July (2004) Lisbon, Portugal, Eng. Fail. Anal., 12, pp. 851–859

37. Ezrin, M., Lavigne, G., Dudley, M., Pinatti, L., Case studies of plastics failure related to molecular weight or chemical composition Soc. Plast. Eng. ANTEC May (2005) pp. 3469–3474, Boston, MA

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38. Ezrin, M., Lavigne, G., Adhesion failures of plastics bonded to various materials Soc. Plast. Eng. Joining of Medical Plastics Conf., October (2005) Paper No. 1, Providence, RI

39. Ezrin, M., Lavigne, G., Unexpected and unusual failures of polymeric materials Soc. Plast. Eng. ANTEC May (2006) pp. 2004–2011, Charlotte, NC

40. Ezrin, M., Lavigne, G., Unexpected and unusual failures of polymeric materials Second Int’l Conf. On Engineering Failure Analysis, Eng. Fail. Anal., Toronto, September (2007) 14, pp. 1153–1165

41. Ezrin, M., Boston’s Big Dig fatal epoxy adhesive failure Soc. Plast. Eng. ANTEC, May (2008) pp. 2327–2331, Milwaukee, WI

42. Ezrin, M., Environmental, recycling and health aspects of plastics failure Soc. Plast. Eng. ANTEC May (2008) pp. 713–722, Milwaukee, WI

43. Ezrin, M., Fracture of plastic parts in water service, Soc. Plast. Eng. ANTEC June 2009, pp. 664–667, Chicago, IL

44. Ezrin, M., Failure of Human Biopolymers Soc. Plast. Eng. ANTEC June (2009) pp. 208–219, Chicago, IL

45. Ezrin, M., Failure of Human Biopolymers—II Soc. Plast. Eng. ANTEC May (2010) pp. 1289–1293, Orlando, FL

46. Ezrin, M., Fundamentals and practice of plastics failure analysis Soc. Plast. Eng. ANTEC May (2011) Boston, MA

47. Ezrin, M., Fundamentals and practice of plastics failure analysis Soc. Plast. Eng. EUROTEC November (2011) Barcelona

1.14.2 Plastics Analysis

48. Ezrin, M., Claver, G. C., Characterization of thermosetting resin curing behavior by thermal analysis under pressure Applied Polymer Symposia 8 (1969) Int’l Symp. on Polymer Characterization, Interscience, p. 159

49. Ezrin, M., Harten, J., Thermogravimetric analysis screening of fl ame retardant thermo-plastics for molding safety Soc. Plast. Eng. ANTEC (1981) pp. 188–189, Boston, MA

50. Krause, A., Lange, A., Ezrin, M., Plastics Analysis Guide--Chemical and Instrumental Methods (1983) Hanser Publishers, Munich

51. Ezrin, M., Lavigne, G., Plastics analysis by pyrolysis GC/MS Soc. Plast. Eng. ANTEC (1997) pp. 2305–2309, Toronto

52. Ezrin, M., Lavigne, G., Polymer analysis by thermal desorption and pyrolysis GC/MS, Federation of Analytical Chemistry and Spectroscopy Societies (FACSS), October (1997) Providence, RI

53. Ezrin, M., Plastics Analysis–The engineer’s resource for troubleshooting product and process problems and for competitive analysis, Plastics Engineering (2002) 58 (2), pp. 40–55

54. Ezrin, M., Lavigne, G., Analysis of silicone polymers at trace levels by pyrolysis gas chromatography/mass spectroscopy Soc. Plast. Eng. ANTEC May (2002) pp. 2046–2050, San Francisco, CA

55. Ezrin, M., Lavigne, G., Aromatic hydrocarbon content of plastic packaging materials Soc. Plast. Eng. ANTEC May (2003) pp. 2015–2017, Nashville, TN

56. Ezrin, M., Lavigne, G., Aromatic hydrocarbon content of common plastic packaging materials Soc. Plast. Eng. Global Plastics Environmental Conference, February (2004) Paper abstract No. 27, Detroit, MI

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57. Lavigne, G., Ezrin, M., A syringeless injection device for the introduction of solids and liquids into a split/splitless capillary injection port Pittsburgh Conference, March (2004) Chicago, IL

58. Ezrin M., Lavigne, G., Dudley, M., Pinatti, L., Leek, F., The role of analytical and physical methods in plastics failure analysis Soc. Plast. Eng. ANTEC May (2007) pp. 2777–2782, Cincinnati, OH

1.14.3 Electrical Insulation

59. Katz, C., Dima, A., Zidon, A., Ezrin, M., Zengel, W., Bernstein, B., Emergency overload characteristics of extruded dielectric cables operating at 130 °C and above, IEEE Trans-actions on Power Apparatus and Systems (1984) Vol. PAS–103, No. 12, pp. 3454–3463

60. Ezrin, M., Electrical insulation research at the University of Connecticut, Conference Proceedings of the non-ferrous electrical division meeting, Wire Association Inter-national, Providence, RI, May 21–23 (1984) pp. 24–40

61. Ezrin, M., Gartner, J., Test method for evaluation of the resistance of fi berglass rods to combined mechanical and chemical stress, IEEE Transactions on Power Apparatus and Systems (1984) Vol. PAS–103, No. 9, pp. 2741–2745

62. Ezrin, M., Seymour, D., Katz, C., Dima, A., Bernstein, B., Thermal response of cable insulation, shield and jacket materials aged at 130 °C and above Conf. Record of the 1986 IEEE International Symposium on Electrical Insulation, pp. 47–49, Washing-ton, DC

63. Ezrin, M., Seymour, D., Characterization of unforeseen eff ects of thermal aging on power distribution cable insulation Soc. Plast. Eng. ANTEC (1988) pp. 889–892 Atlanta, GA

64. Ezrin, M., Bernstein, B., Application of a sealed tube test to the study of degraded insulation resulting from thermal aging of cables with PVC jacke Conference Record of the 1988 IEEE International Symposium on Electrical Insulation, June (1988) pp. 215–218, Boston, MA

65. Ezrin, M., Gruchawka, S., Applications of thermal analysis to electrical insulation Eastern Analytical Symposium, November 17 (1993) Somerset, NJ

66. Ezrin, M., Lavigne, G., Case studies of failure of polymeric electrical insulation Soc. Plast. Eng. ANTEC May (2001) pp. 2869–2872, Dallas, TX

1.14.4 Solar Panel Encapsulant Discoloration

67. Ezrin, M., Lavigne, G., Klemchuk, P., Holley, W., Agro, S., Galica, J., Thomas, L., Yorgensen, R., Discoloration of EVA encapsulant in photovoltaic cells Soc. Plast. Eng. ANTEC (1995) pp. 3957–3960, Boston, MA

68. Ezrin, M., Lavigne, G., Klemchuk, P., Pickering, J., Holley, W., Galica, J., Agro, S., Nelson, W., Wu, Q., Further studies of discoloration of EVA encapsulant in photo-voltaic modules Soc. Plast. Eng. ANTEC (1996) pp. 3260–3264, Indianapolis, IN

69. Klemchuk, P., Ezrin, M., Lavigne, G., Holley, W., Galica, J., Agro, S., Investigation of the degradation and stabilization of EVA-based encapsulant in fi eld-aged solar energy modules, Polymer Degradation and Stability (1997) 55, pp. 347–365

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1.14.5 Plastics Recycling

70. Ezrin, M., Wyatt, E. D., Lavigne, G., Garton, A., Quantifi cation and control of contaminants in recycled HDPE, Soc. Plast. Eng. ANTEC (1994) pp. 2922–2926, San Francisco, CA

71. Ezrin, M., Lavigne, G., Dinger, P., Identifi cation and semiquantitative analysis of organic compounds in recycled dairy grade HDPE Soc. Plast. Eng. ANTEC (1995) pp. 3715–3719, Boston, MA

72. Klingelhofer, E. D. W., Ezrin, M., Weiss, R. A., Diff usion of hazardous contaminants in recycled high density polyethylene Soc. Plast. Eng. ANTEC (1995) pp. 3710–3714, Boston, MA

73. Ezrin, M., Lavigne, G., Analysis of organic compounds in recycled dairy grade HDPE by thermal desorption gas chromatography/mass spectroscopy Soc. Plast. Eng. Annual Recycling Conference, November 2–3 (1995) pp. 103–110, Akron, OH

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1 a preliminary look at the nature, causes, and ... · naturally, long before we started making...

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