Environmental stress cracking the plastic killer researchgate. Jansen, stork technimet abstract four case studies are presented to illustrate environmental stress cracking esc within automotive components. When force is applied to plastic, it travels along the polymer chains causing molecules to strain to remain in contact. Environmental stress cracking esc is a welldocumented phenomenon in plasticpolymer components and can occur when a polymer component is exposed. The chemical simply accelerates the stress cracking. Environmental stress cracking esc is widely regarded as the leading cause of plastic. According to astm d883, stress cracking is defined as an external or internal crack in a plastic caused by tensile stresses less than. Environmental stress cracking esc is a welldocumented phenomenon in plastic polymer components and can occur when a polymer component is exposed to an aggressive chemical agent while under tensile stress, whether residual or applied. Re your query on environmental stress cracking of plastics, the corrosion resistance data given out by the manufactures sometimes indicate that a given thermoplastic in a given environment at a given temperature may not be suitable. Environmental stress crack resistance of polyethylene. Pdf environmental stress cracking is involved with some. Environmental stress cracking esc is one of the most common causes of unexpected brittle failure of thermoplastic especially amorphous polymers known at present. Environmental stress cracking in polyethylene takes place because of interlamellar failure, which in turn is caused by relaxation of tie molecules. Environmental stress crack resistance escr is a vital property required in plastics for its longevity.
Esc occurs in conjunction with internal and external stresses on a plastic. In environmental stress cracking, the presence of an esc agent accelerates the effect of stress on a polymer material. If the plastic is under stress, it may also experience environmental stress cracking, which can be defined as the crazing and cracking that may occur when a plastic. In the escr test, tensile bars are bent to specific strain levels typically 0. Chemical attacks are sometimes considered esc environmental stress cracking when related to vulnerabilities in the plastics structure. This phenomenon is characterized by the presence of brittle fracture, multiple cracks, smooth morphology. Influencing the environmental stress cracking resistance of. Standard test method for environmental stresscracking of ethylene plastics 1. Environmental stress cracking esc is the leading cause of plastic components failure. The stress at which esc cracking occurs is often well below the nominal fracture stress of the. According to astm d883, stress cracking is defined as an external or internal crack in a plastic caused. Combinations of certain environments, coupled with stress andor strain upon the material, cause stress cracking or crazing of the polycarbonate sheet. In environmental stress cracking in plastics, an environmental liquid seeps into the plastic, resulting in swelling, and this causes a crack to occur. Evaluating environmental stress cracking of medical plastics.
It is the premature embrittlement and subsequent cracking of a plastic due to the simultaneous and synergistic action of stress and contact with a chemical agent. The third type of attack is often the most difficult to predict since environmental conditions dictate whether or not the plastic will be affected. Aggressive exposure of plastics to chemical contaminants to detect instances of environmental stress cracking esc 1, 2. Environmental stress cracking the the chemical agent does. Environmental stress crazing 799 ntetradecane hexane isooctane 1400 1600 600 1200 nhexane 7. Jansen stork technimet new berlin, wisconsin e nvironmental stress cracking esc is a phenomenon in which a plastic resin is degraded by a chemical agent while under stress, and it is the leading cause of plastic component failure. The results reported here confirm that environmental stress cracking phenomena in plastics depend on the size and shape of the test liquids molecules as well as their hansen solubility parameters hsp relative to those of the polymer. Environmental stresscracking has been found to occur most readily under such.
It is one of the most common causes of unexpected brittle failure in thermoplastic. Sabic unveils its new lnp elcres crx pc copolymers that. Environmental stress cracking in plastics rj lee group. Plastics will exhibit environmental stress cracking when exposed to an aggressive chemical environment if and only if a tensile stress is present. Chemical resistance chart for plastics an indepth look. It is a solventinduced failure mode, in which the synergistic effects of the chemical agent and mechanical stresses result in. Environmental stress cracking resistance of plastics. Esc is the consequence of a combination of mechanical stress and exposure to an aggressive chemical. Environmental stress cracking esc is not the result of the continual battle that the plastics industry has in convincing environmentalists and politicians that plastics can be the solution to environmental problems and not the cause esc is the consequence of a combination of mechanical stress and exposure to an aggressive chemical.
Environmental stress crack resistance escr testing of. The goal of this article is to provide a framework for evaluating the suitability of a plastic for medical uses in terms of its stress crack behavior. Investigations on environmental stress cracking resistance. Environmental stress cracking the the chemical agent. Its the reason you cant put stickers on your motorbike helmet.
Environmental stress cracking in plastics rj lee group, inc. Environmental stress crack resistance escr testing of plastics. Esc is a failure mechanism whereby a plastic resin is effected by a chemical. Because the mechanisms of failure for solvent attack and environmental stress cracking are so different, the means of optimizing material parameters are different as well. Solvent stress cracking, which is often incorrectly referred to as environmental stress cracking, can occur in almost any plastic. Standard test method for environmental stresscracking of. Environmental stress cracking esc is not the result of the continual battle that the plastics industry has in convincing environmentalists and politicians that plastics can be the solution to environmental problems and not the cause. Our strategy will be to examine, in some detail, the roles of the three critical components of environmental stress cracking.
Reduce environmental stress cracking esc of your plastic parts by better predicting failure occurrence and implementing adequate prevention measures. Environmental stress cracking is involved with some 25% of plastic part failures. According to astm d883, stress cracking is defined as an external or internal crack in a plastic caused by tensile stresses less than its shortterm mechanical. Prediction of environmental stress cracking in plastics with. This month we want to conclude the discussion with a few more case studies and then discuss tests and material selection techniques that can keep us out of trouble with this challenging problem. Environmental stress crack resistance of polyethylene stress crack reagent concentration in the case of the most commonly used stress crack reagent, igepal co630, as the concentration of water in the stress cracking media increases, the faster the esc onset. Environmental stress cracking an overview sciencedirect topics. It is called environmental stress cracking and basically it means that solvents cause the material to crack due to built in stresses in the polycarbonate. Environmental stress cracking esc is a welldocumented phenomenon in plasticpolymer components and can occur when a polymer component is exposed to an aggressive chemical agent while under tensile stress, whether residual or applied. Evaluating environmental stress cracking of medical. Smithers provides an overview of environmental stress cracking for polymer materials, and how test programs can help reduce or even prevent failure. The mechanism of environmental stress cracking esc of amorphous polycarbonate in isopropyl alcohol, ethylene glycol monomethyl ether and methanol. Environmental stress crack resistance of polyethylene introduction to environmental stress cracking and escr over the past decade, highdensity polyethylene hdpe materials have improved significantly and now meet more stringent performance standards.
The lenses were injection molded from a polycarbonate resin and. However, it usually occurs in amorphous thermoplastics. By environmental stress cracking, we understand a failure in which materials in contact with a fluid are subjected to stress. Because of this, environmental stress cracking and creep rupture are parallel failure mechanisms. Standard test method for environmental stress crack. This concept may contribute to environmental stress crazingcracking but is generally believed to be a minor effect in consideration of the overall mechanism particularly where severe stress cracking occurs. Repeated cleanings can cause environmental stress cracking esc that can lead to part failure. Environmental stress cracking esc, a brittle failure mode of plastic parts under. Environmental stress cracking in polyethylene takes place because of interlamellar failure, which.
How to prevent stress cracking what is stress cracking. Based on this, for the purpose of capturing the formation of that radical, we carried out an observation of the phenomenon of envi. This problem is well known and is called environmental stress cracking. The presented cases illustrate how the failure analysis process. D541914a standard test method for environmental stress crack resistance escr of threaded plastic closures environmental stress crack resistance threaded plastic closures. At creative mechanisms, we have used polycarbonate in a number of applications across a range of industries. Environmental stress cracking esc is a premature failure of a polymer exposed to a fluid, under stress which is much less than its yield stress. The tensile stress may be applied externally or may simply be a consequence of residual, or moldedin, stresses. Esc is a very important mode of plastic component failure. Simultaneous action of stress and strain on plastics in contact with specific fluids causes the onset of cracking and embrittlement of plastic known as environmental stress cracking. Environmental stress cracking may account for around 1530% of all plastic component failures in service. The mechanisms of environmental stress cracking proposed in the literature will be discussed in detail. Significantly, in the absence of the chemical the plastic would undergo stress cracking in air, also known as creep rupture, given sufficient time. Investigations on environmental stress cracking resistance of.
Often moisture in the material, weak welding, or inmold stress can result in a dramatically weakened product, shortening the projected lifespan of the workpiece. Oct 25, 2011 stress cracking is the most common cause of plastic product failure and is particularly difficult to manage since the time frame of this type of failure is typically weeks or months. Polycarbonate cracking polymer engineering engtips. Environmental stress cracking resistance of polyethylene.
Plastic failure through environmental stress cracking esc, the plastic killer, is a frequent cause of field failures by jeffrey jansen the madison group, madison, wisconsin, usa environmental stress cracking esc is considered a lead ing cause of plastic part failure. In last months article we defined the terms environmental stress cracking and solvent stress cracking, briefly explained the mechanisms involved, and provided a couple of examples of actual case studies. Environmental stress cracking esc is considered a leading cause of plastic part failure. It is a lighter alternative to glass and a natural uv filter, so it is often used in eyewear. A materials resistance against this type of failure is called environmental stress cracking resistance escr. Therefore, its especially important to identify common types of failure and their underlying causes. In this mechanism the solvent actually replaces polymer at the surface of the part. When the stress profile within a plastic part is known, adjustments in the process, material, or part design may be. Under the conditions of the test method, high local multiaxial stresses are developed through the introduction of a controlled imperfection 2, 3. Polycarbonate is an incredibly useful plastic for applications requiring transparency and high impact resistance. A guide to chemical resistance of polycarbonate sheet. Environmental stress cracking environmental resistance.
Prediction of environmental stress cracking in plastics. Under certain conditions of stress and in the presence of environments such as soaps, wetting agents, oils, or detergents, ethylene plastics. We postulated that at that time a radical may form. Some performance evaluation tests that once took only days to run now take months with todays. Chemical resistance chart for plastics an indepth look at. However, it is also extremely sensitive to liquids that come in contact with it and will become weakened and crack.
Esc is the occurrence of cracking in a polymer by contact with a liquid or vapour environment and stress. Here, the environmental stress cracking esc is considered as the main cause for the failure of plastics. The manufacturing process itself is crucial when it comes to preventing plastic failure. Pdf stress cracking of polycarbonate exposed to sunscreen. When a part or product fails, the consequences can be severe. Environmental stress cracking an overview sciencedirect. Many experimental works were done before in an effort to predict experimentally the esc potential of a fluid in different polymers. Stress cracking is the most common cause of plastic product failure and is particularly difficult to manage since the time frame of this type of failure is typically weeks or months. According to astm d883, stress cracking is defined as an external or internal crack in a plastic caused by tensile stresses less than its shortterm mechanical strength. With force and time, crazing or stress cracking occurs. Plastic failure through environmental stress cracking. The behavior of other, untested liquids can be estimated from hsp correlations based on a limited number of test liquids. Since this is responsible for 15% of all failures of plastics components, environmental stress cracking has long been the subject of intensive research.
Definition of environmental stress cracking esc environmental stress cracking esc in plastics means the failure at about room temperature due to continuously acting external andor internal stresses in the presence of surface active substances known as stress cracking agents such as alcohols, soaps, dyes, agents containing moisture. Environmental stress cracking esc is a phenomenon in which a plastic resin is degraded by a chemical agent while under stress, and it is the leading cause of plastic component failure. Chemical attacks are sometimes considered esc environmental stress cracking when related to vulnerabilities in the plastic s structure. Reducing environmental stress cracking in plastic parts. The polymer chains eventually creep toward the pull and deform. High levels of stress also lower a products impact strength and can contribute to environmental stress cracking and diminished performance at high or cycling temperatures. Whereas some cracking results from excessive loads, or from thermal or uv degradation, a large percentage of plastic part failure results from a phenomenon termed environmental stress cracking esc, which is the result of an external chemical acting on a plastic part that contains internal stresses. This month we want to conclude the discussion with a few more case studies and then discuss tests and material selection techniques that.