Chemical exposure may result in either physical degradation stress cracking, crazing, swelling and discoloration or chemical attack reaction of chemical with polymer and loss of. This means that polycarbonate, polyacrylonitrilebutadienestyrene, and. Environmental stress cracking environmental resistance. Stress cracking sc and environmental stress cracking esc are two main mechanisms for cracked polycarbonate parts 1 2 345678. A facet of that work involved demonstrating that the composition of the gasoline may change during testing through preferential evaporation of volatile components, which, in turn, can affect the results. It became apparent that environmental stress failure was an achilles heel for these otherwise high performance materials and exposure to application environments needed to be strongly considered. Polycarbonate cracking polymer engineering engtips. 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. There are factors other than viscosity that can also affect the stress cracking problem. Smithers provides an overview of environmental stress cracking for polymer materials, and how test programs can help reduce or even prevent failure. 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. Plastic failure through environmental stress cracking. Environmental stress cracking, often referred to as esc, causes a stressed plastics part to become brittle and crack when in contact with a wide range of fluids that act as stress cracking agents.
Environmental stress crack resistance escr is a vital property required in plastics for its longevity. Environmental stress cracking esc is widely regarded as the leading cause of plastic. It is the combination of stress and fluid contact that causes failure to occur much earlier than either component could achieve in isolation, if at all. Environmental stress cracking in plastics rj lee group. Abstract polycarbonate pc is an engineering polymer which presents interesting properties. The problem lies, in part, in the definition of stress cracking. This broad term reflects the role of environment plays in the cracking process and the terms now covers all the following. At a high enough stress a polymer will crack even with a poorlycompatible solvent. Environmental stress cracking the the chemical agent does. The mechanical behavior and environmental stress cracking esc resistance of the nanocomposites were investigated. Polycarbonate is sensitive not just only to solvent cracking, such as those seen on. The bent strip test is a constant strain test, but polyethylene relaxes when strained. The mechanism of environmental stress cracking esc of amorphous polycarbonate in isopropyl alcohol, ethylene glycol monomethyl ether and methanol.
Environmental stress cracking esc is the most common failure mechanism, whereby mainly organic fluids accelerate crack initiation and growth under conditions of applied or processedin stress. Chemical resistance and stress cracking in polyurethanes. Environmental stress crack resistance of polyethylene. This type of cracking typically involves brittle cracking, with little or no ductile drawing of the material from its adjacent failure surfaces. Environmental stress crazing 799 ntetradecane hexane isooctane 1400 1600 600 1200 nhexane 7. Jun 28, 20 this article discusses polyurethane benefits and challenges, and also provides a test case for a proprietary aliphatic polycarbonate alc polyurethane. There is much printed information available regarding stress crazing in thermoplastic sheet products. Environmental stress cracking is one of the most common causes of unexpected brittle failure of thermoplastic polymers known at present. Environmental stress cracking esc or stress corrosion cracking scc seemed the most likely cause of the brittle cracks seen in the retained samples, but no records had been kept by the hospital of what fluids the connectors had made contact during service. Standard test method for environmental stresscracking of. Prediction of environmental stress cracking in polycarbonate by molecular modeling. The environmental crazing from a central hole in extruded polycarbonate sheets, using ethanol as a crazing liquid, was studied. Environmental stress crack resistance escr testing of plastics. The potential for environmental stress cracking is of paramount concern when plastics are.
Introduction plastic components are used in various kinds of equipment and machinery, but depending on the environmental factors involved, various kinds of degradations may arise. 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. Some plastics such as abs, acrylic, polycarbonate, and polystyrene are more susceptible to stress cracking. Environmental stress cracking can take place through continuous crack growth or via a stepwise progressive mechanism of cracking and arrest, depending on the molecular structure of the plastic, the composition of the chemical agent, the level of stress, and other environmental conditions.
A stress analysis was made to analyse the criteria for craze initiation and growth. Environmental stress cracking esc resistance of polycarbonates i. Among these is environmental stress cracking, which. An assessment of polymer resistance to potential esc agents is undertaken during the design stage of development, where an appropriate test program can measure the impact of these primary environments on the material. Environmental stress cracking in plastics 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. It has been estimated that 15% of all failures of plastic materials in commercial use are related to environmental stress cracking esc 3. In environmental stress cracking, the presence of an esc agent accelerates the effect of stress on a polymer material. It is one of the most common causes of unexpected brittle failure in thermoplastic. The two terms were collectively known as stress corrosion cracking which was in turn replaced by environmentsensitive cracking or environmental cracking. Environmental stress crack resistance escr testing of. The behavior of other, untested liquids can be estimated from hsp correlations based on a limited number of test liquids.
Environmental stress cracking may account for around 1530% of all plastic component failures in service. Since this is responsible for 15% of all failures of plastics components, environmental stress cracking has long been the subject of intensive research. Initial efforts to develop an esc test method for polymer blends were. Often we tend to group all the problems into the environmental category, but in reality most of the field problems we see have to do with solvent stress cracking. Furthermore, a fracture mechanics study under dry conditions and in the presence of the aggressive environment was done. Environmental stress cracking in plastics rj lee group, inc. The lenses were injection molded from a polycarbonate resin and.
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. Revised stresscracking resistance of polycarbonate in. Evaluating environmental stress cracking of medical plastics. Materials 2 medical plastics 3 chemical resistance and stress cracking in polyurethanes aliphatic polycarbonate polyurethanes demonstrate broad chemical resistance for in vivo.
This present study is confined to the environmental stress cracking resistance of polycarbonate. Polymethylmethacrylate, environmental stress cracking, chemiluminescence, radical 1. Prediction of environmental stress cracking in polycarbonate by. This month we want to conclude the discussion with a few more case studies and then discuss tests and material selection techniques that. Because of this, environmental stress cracking and creep rupture are parallel failure mechanisms. 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. Esc is a failure mechanism whereby a plastic resin is effected by a chemical agent while simultaneously under tensile loading. Polymers for advanced technologies 2014, 25 12, 14331438. Environmental stress cracking is involved with some 25% of plastic part failures. In particular, the esc of polymer blends was studied to gain a deeper understanding of the role of phase miscibility, blend morphology, and crystallinity on failure.
The effect of polymer blending on environmental stress. Environmental cracking results from the conjoint action of three components. Stress concentration can cause polycarbonate parts. The data, based on the critical stress intensity factor in and away from the stress cracking environment, explains the behavior of polycarbonate abs blends relative to the modified polyphenylene oxide system. Evaluating environmental stress cracking of medical.
There are factors other than viscosity that can also affect the stresscracking problem. This stress relaxation allows testing to run without failure for very long periods 1,500 hours. Plastics will exhibit environmental stress cracking when exposed to an aggressive chemical environment if and only if a tensile stress is present. A common misconception about environmental stress cracking is that it involves. For example, copper and its alloys are susceptible to ammonia compounds, mild steels are susceptible to alkalis and stainless steels are susceptible to chlorides. The environmental stress crazing of polycarbonate springerlink. This problem is well known and is called environmental stress cracking. Glassy amorphous thermoplastics are most susceptible, and the most common fluids that cause the problem are lubricants, adhesives, corrosion inhibitors, surfactants, cleaning agents, solvents, and paints. However, it is also extremely sensitive to liquids that come in contact with it and will become weakened and crack. 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. Plasticizer chemical type, level of use, polarity, and severity of environmental conditions all play a role in the development of cracking in stressed polycarbonate. Crazing can be induced at moderate to high stress levels by low molecular weight hydrocarbons. 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. This material has been also used in medical devices, which is frequently exposed to gamma radiosterilization and to chemical agents.
A few plastics, among them pet and polycarbonate, can be entirely. Chemical resistance and stress cracking in polyurethanes arlo n. Environmental stress cracking of polycarbonate catheter. This may produce significant changes in polymer structure, leading to failure in service. Environmental stress cracking of polycarbonate and a. The base lens material was tested via dsc and a glass transition. A guide to chemical resistance of polycarbonate sheet. The environmental stress crack resistance of polycarbonate. Abstract polycarbonate pc nanocomposites containing different nano. Environmental stress cracking an overview sciencedirect. Polycarbonate pc nanocomposites containing different nano. Behaviour of polycarbonate in different chemical by determination of the timedependence of stress at constant strains.
The test provides analysis for the materials oxidation and alcohol absorption, as well as its resistance to environmental stress cracking. Environmental stress cracking the the chemical agent. An example of environmental stress cracking on polycarbonate can be seen below. Environmental stress cracking esc is one of the most common causes of unexpected brittle failure of thermoplastic especially amorphous polymers known. Environmental stress cracking refers specifically to a phenomenon. Wyzgoski, prediction of environmental stress cracking of polycarbonate from solubility considerations, journal of applied polymer science, 23, 11531166, 1979. The minimum strains required to cause cracking of polycarbonate upon exposure to several windshield washer fluids were determined.
Environmental stress cracking esc resistance of polycarbonate sio 2 nanocomposites in different media. Your polycarbonate is probably just fine initially but has been exposed to some unsuitable liquid. A recent study indicated that approximately 25% of plastic component failures are associated with esc1. Read the role of surfactant structure and monoethanolamine in the environmental stress cracking of polycarbonate, journal of applied polymer science on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. The type of stress involved with surface crazing is most usually a tensile stress. A detailed investigation of this environmental stress cracking was conducted with one of these fluids which is identified here as fluid a. 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. Polycarbonate pc is an engineering polymer which presents interesting properties. Prediction of environmental stress cracking in plastics. The present work brings about a new approach on environmental stress cracking esc processes elucidation in 100 kgy. Its the reason you cant put stickers on your motorbike helmet. 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.
In general this problem falls into two subcategories. Stress cracking sc and environmental stress cracking esc are two main mechanisms for cracked polycarbonate parts 1 2345678. 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 cracking esc is one of the most common causes of unexpected brittle failure of thermoplastic especially amorphous polymers known at present. This article discusses polyurethane benefits and challenges, and also provides a test case for a proprietary aliphatic polycarbonate alc polyurethane.
The environmental stress cracking esc of polymeric materials was investigated in order to elucidate the fundamental polymer properties leading to failure. 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. Environmental stress crack resistance of polyethylene today, this test is specified less frequently because it is not as aggressive towards modern resins. The present work brings about a new approach on environmental stress cracking esc. 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. The tensile stress may be applied externally or may simply be a consequence of residual, or moldedin, stresses.
Environmental stress cracking esc is considered a lead ing cause of plastic part failure. 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. Environmental stress cracking esc is widely regarded as the leading cause of plastic product failure. Products such as acetone and xylene may cause stress cracking even at very low stress levels and should therefore be avoided. Chemical resistance can be dependent upon exposure time, temperature, stress molded in and any external stress, type of chemical and the chemical concentration. Journal of applied polymer science 2017, 4 43, 45451. Environmental stresscracking has been found to occur most readily under such. Polycarbonate frequently appears in the role of stress crack victim. It should also be noted that stress cracking in abs and polycarbonate has been reported in air in the presence of stress only. Glassy amorphous thermoplastics are most susceptible, and the most common fluids that cause the problem are lubricants, adhesives, corrosion inhibitors. The polycarbonate sample at the top has been placed under stress for over 7 hours with no chemical agent applied, it shows no visual signs of cracking. 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. Its made of polycarbonate and the adhesive in the stickers will ruin the impact resistance of the helmet.
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