Cleaning polycarbonate sheet before vinyl application. 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. Sometimes stress is not visible until the component is subject to loading or exposure to chemicals by the end user. Carbonate stress corrosion cracking acscc inspectioneering. The stress cracking effects were evaluated by solvent absorption, stress relaxation and mechanical testing during solvent exposure. Crazing can be induced at moderate to high stress levels by low molecular weight hydrocarbons. This whitepaper explains the cause and impact of plasticizerinduced stress cracking, as well as the relative stress crackresistance of specialtyformulated rigid pvc versus polycarbonate et al when exposed to pvc plasticizers commonly used in pvc medical tubing applications. Since the introduction of the first 2liter, onepiece pet bottle by continental can co. Aug 01, 2007 since the introduction of the first 2liter, onepiece pet bottle by continental can co. Provides technical data and properties for engineering grade polycarbonate rod and sheet keywords. Environmental stress cracking is involved with some 25% of plastic part failures. Exposure to some solvents can ultimately cause stress cracking or cloud the surface of the exposed plastic. The chemicals listed have been evaluated for lexan according a very stringent ge test method. Molecular degradation many of tuffak properties are determined by the size of its molecules.
The mathematical relationship between outer fiber strain, radius of curvature r and thickness t is. Strips of a plastic, each containing a controlled defect, are placed in a bending rig and exposed to a stress cracking agent. A recent study indicated that approximately 25% of plastic component failures are associated with esc1. Environmental stress cracking is considered to be the most frequent mode of failure of plastic materials. Side notches are made to facilitate the cracking in the main notch. Reference 2 uses the following to describe the chemical resistance of polycarbonate to a solvent. Such myths are either wholly wrong or correct just part of the time. Improvement of environmental stress cracking resistance of polycarbonate by.
This is known as the longterm hydrostatic strength lths. Carbonate stress corrosion cracking acscc is a common problem in the oil and gas production, petroleum refining, and petrochemicalchemical processing industries. Stress cracks or surface crazing near stress concentrators like threads can be a sign of future problems. Esc is a failure mechanism whereby a plastic resin is effected by a chemical agent while simultaneously under tensile loading. The most important factor to consider when drilling lexan sheet products is the heat generated during the actual process. They had been having this issue on a specific part from one of their current suppliers. Measuring residual stress in transparent plastics mddi online. The variation of stress with time was recorded, and the surface cracking was observed. Standard test method for environmental stresscracking of.
Stress concentration can cause polycarbonate parts. Chemical exposure can result in discoloration, softening, swelling, crazing, cracking or loss of properties of the thermoplastic. Testing residual stresses and molecular orientation throughout a product provide important information about how that product will perform. Test method the strain in the test environmental stress. Li b a department of macromolecular science and the key laboratory of molecular engineering of polymers, fudan university, shanghai, 200433, china b shanghai koito automotive lamp co.
It can typically be formed at room temperature without cracking or breaking, similar to aluminum sheet metal. According to chemical resistance of plexiglass acrylic alcohol is not as aggressive as you mention with plexiglass acrylic. If a plasticized pvc tube is mounted on a stressfree polycarbonate pipe, for instance, the. Lexan 9600 sheet product datasheet description typical. Rapra in the united kingdom states that in nearly onethird of all failed plastic applications the problem is stress cracking.
The amount of crystalline content in the container depends on the rate of cooling. Its the reason you cant put stickers on your motorbike helmet. This research studies the stress cracking of polycarbonate plastic by a variety of solvents and solvent blends. Environmental stress cracking escr is the formation of cracks in a part when exposed to chemicals, if the parts have residual stress in them after molding. Analysis of polycarbonate stress cracking and cleaning. Plasticizers within pvc, such as phthalates can trigger stress cracking and result in damage to the polycarbonate. Because standard test methods for measuring escr on plastics take such a long.
Environmental stress cracking esc is one of the most common causes of unexpected brittle failure of thermoplastic especially amorphous polymers known at present. The mixed solvent test for polycarbonate is well developed. Astm d2561 17 standard test method for environmental stress. It is important to feed the sheet against the rotation of the router bit and to provide a fence for sizing when making straight cuts. A list of approved paint systems and suppliers is available on request.
For example, the test method astm f48402 stress crazing of acrylic plastics in contact with liquid or semiliquid compounds uses flexural stress levels of 3,000, 3,500, and 4,500. Environmental stress crack resistance of polyethylene this test method is shown in figure 3. Lexan cracking plastics engineering general discussion. Unlike most other plastics, polycarbonate is capable of undergoing large hot moulding deformations without cracking or breaking. High stress levels in plastic are a common cause of component field failures.
The exposed bars were then put in contact with ethanol, a stress cracking agent of pmma. Plastic stress test protocols connecticut plastics. Plasticizerinduced stress cracking of rigid pvc vs. The tensile bars suggested for use in this test are injection molded and measure 8. It is associated with the phenomenon of crazing and solvent plasticization of the polymer. A laminate comprising a sheet of polycarbonate laminated to another sheet comprising, on a weight basis, a 30 to 90% polyvinyl butyral and b 70 to 10% thermoplastic polyurethane, containing a plasticizing amount of one or more c 2 c 5 alkanediols or diethylene glycol. Complementary tests were done by size exclusion chromatography, uvvisible. Stress cracking of polycarbonate exposed to sunscreen. In a set of experiments, certain cleaning solvents were. The bent strip method described in astm d1693 will be described below as the environmental stress cracking test method for the molded plate. Environmental stress cracking of polypropylene springerlink. The results confirmed the high deterioration of pmma by both gamma radiation and the active fluid. 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. Us5212014a polycarbonate sheet laminated to plasticized.
Painting lexan 9600 sheet is ideally suited for use with a wide variety of modern decoration techniques. Basic understanding of stress cracking in hdpe products. Evaluation of residual stress in molded resin jfe techno. The use of polycarbonate in automotive applications is limited to low stress applications. Another feature of polycarbonate is that it is very pliable. A number of myths have arisen as to the causes and remedies for stresscracking. Plastic failure through environmental stress cracking. Environmental stress cracking esc is widely regarded as the leading cause of plastic product failure. Pdf stress cracking of polycarbonate exposed to sunscreen. Acscc is a form of alkaline stress corrosion cracking that often occurs more aggressively at higher ph and high concentrations of carbonate solutions. If the molded part is completely stress free or is subject solely to compressive stress, then no stress cracking will occur.
Feeding makrolon polycarbonate sheet at excessive rates can cause vibration and cracking. Other anecdotal data from experienced plastic part designers tends to echo. Environmental stress cracking the the chemical agent. Investigations on environmental stress cracking resistance of. One example is the contact between polycarbonate and plasticized pvc.
Although deformation may be simpler with the application of heat, even small angle bends are possible without it. Constantstress test can be another contributor to stresscracking. The number of specimens that crack over a given time is. This makes it an excellent plastic for prototyping applications where transparent or electrically nonconductive parts are needed, which cannot otherwise be made from sheet metal. Its made of polycarbonate and the adhesive in the stickers will ruin the impact resistance of the helmet. Astm d 1693 describes a test for evaluating the stresscrack resistance of ethylene plastics in environments such as soaps, wetting agents, oils, or detergents. Environmental stress crack resistance of polyethylene. 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.
The results of this research can be used to develop targeted replacements for 1,1,1trichloroethane and cfc1, replacements that have equivalent or better compatibility with polycarbonate plastics. For this reason, use caution when using solvents to clean the surface of polycarbonate. Another variable to be considered in polycarbonate stress crack testing is solvent application method. Stress cracking and photodegradation behavior of polycarbonate. Diagnose it before it ruins your parts residual stress is an inherent result of plastics manufacturing processes and occurs when molten polymer is cooled and shaped. Possibilities of why a polycarbonate pc part is cracking. The effect of injection moulding processing parameters on the. Evaluating environmental stress cracking of medical plastics. Products such as acetone and xylene may cause stress cracking even at very low stress levels and should therefore be. Fatigue crack propagation in polycarbonate materials technology. 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.
While crystallinity provides strength, it also can lead to cracking. Test fixtures should, of course, be thoroughly cleaned after each test series. To explore the possibility of using surface coating to reduce environmental stress cracking esc of transparent polycarbonate pc parts, silicone coated and sio 2 coated pc were tested in a selfmade threepoint bending apparatus in the presence of ethanol. Astm d 1693 describes a test for evaluating the stress crack resistance of ethylene plastics in environments such as soaps, wetting agents, oils, or detergents. The stress intensity factor k for a single edge notched specimen is determined by. I am worried about flame polishing inducing stress in the component. Environmental stress crack resistance of polyethylene under.
Makrolon polycarbonate sheet can be cut using industrial. Since some of these materials can cause environmental stress cracking, please consult sabic innovative plastics for advice on specific applications. Environmental stress cracking esc is the premature cracking of a polymer due to the combined action of a stress and a fluid. Stress cracking sc and environmental stress cracking esc are two main mechanisms for cracked polycarbonate parts 1 2 345678. In this test, strips of a plastic are positioned in a fixed flexural strain and exposed to a stresscracking agent for a predetermined period. The applied stress is plotted versus the timetofailure on a double logarithmic scale. As little as 10 percent glass fiber can reduce problems with stress cracking in materials like polycarbonate and polysulfone. Stress from fasteners, plastic welding and molding render polycarbonate susceptible to stress corrosion cracking when it comes in contact with certain accelerants such as salt water and plastisol.
The applied stress is plotted versus the timetofailure on a. Products such as acetone and xylene may cause stress cracking even at very low stress levels and should therefore be avoided. And finally, as is the case with so many properties, molecular weight is critical. Hdpe is a semicrystalline material, with no crystals in the melted state. Combinations of certain environments, coupled with stress andor strain upon the material, cause stress cracking or crazing of the polycarbonate sheet. Painting lexan f6000 sheet is ideally suited for use with a wide variety of modern decoration techniques. A guide to chemical resistance of polycarbonate sheet. The fatigue crack propagation tests are carried out with a force controlled sinusoidal. Polycarbonate technical properties data sheet engineering grade author.
Revised stresscracking resistance of polycarbonate in. Since variance of any of these factors can change the environmental stress crack resistance of the container, the test results are representative only of a given test performed under defined conditions in the laboratory. Analysis of polycarbonate stress cracking and cleaning solvent. Escr testing can also be performed using tensile bars that are cut from sheet stock or. Aside from being difficult to predict or test for, stress cracking is. We recently had been asked by a potential customer why a polycarbonate would crack postmolding. Polycarbonate technical properties data sheet engineering grade. Besides the nature and concentration of the contact medium, the appearance of stresscracking effects is influenced by the following factors. The presence or absence of residual stresses is a major concern in the production of plastics for applications such as medical devices and packaging, instrument manufacturing, optical components, and others. Your polycarbonate is probably just fine initially but has been exposed to some unsuitable liquid. Learn about a wide range of highperformance polycarbonate resins and polycarbonate blends with outstanding properties along with dedicated cae support to help you simulate and achieve numerous different surface effects, textures and colors. This problem is well known and is called environmental stress cracking. Stress cracking is one of the most common problems associated with field failures in plastic products.
Specimens are machined directly from pipe or from a molded plaque. Strips of a plastic, each containing a controlled defect, are placed in a bending rig and exposed to a stresscracking agent. Lexan f6000 sheet product datasheet description typical. Since variance of any of these factors can change the environmental stresscrack resistance of the container, the test results are representative only of a given test performed under defined conditions in the laboratory. Investigations on environmental stress cracking resistance.
It involves varying concentrations of npropyl alcohol as the inert ingredient and toluene as the stress crack agent. The chemicals listed have been evaluated for lexan according a very stringent getest method. First, key set points like the dryer settings were not included in the process sheets. Polycarbonate cracking polymer engineering engtips. Test method the strain in the test environmental stress cracking of plastics h. Stress crack will only develop, however, if tensile production andor are applied from the outside. Improvement of environmental stress cracking resistance of. It is important to have an understanding of the amount of stress used in any given test to better evaluate liquids or cleaners that may cause crazing. But, we have to signal that acrylics is a big family of polymers thermoplastics or thermosets derived from acrylic acid. The stress cracking behaviour of polymethyl methacrylate. Under the conditions of the test method, high local multiaxial stresses are developed through the introduction of a controlled imperfection 2, 3. A single notch cut into the test specimen acts as a crack initiation point. The recommended procedure for cleaning polycarbonate is to wash it with warm water and a little nonabrasive detergent, such as 409 cleaner or either. Environmental stress cracking the the chemical agent does.
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