Hdpes are classified as either homopolymers which are stiffer, and copolymers which are more stress crack resistant. 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. Some copolymers of ldpe are available with improved stress crack resistance. Environmental stress cracking may account for around 1530% of all plastic. Grace hsuan, jy zhang and wk wong department of civil, architectural and environmental engineering, drexel university, philadelphia, usa abstract the 100year stress crack resistance scr of corrugated hdpe pipes was evaluated using a 600 mm diameter pipe. Corrugated highdensity polyethylene hdpe pipe 36 in. Environment stress cracking of hdpe products is quite common due to its semi crystalline nature which gets attacked due to chemicals present in the environment. Additionally, polypropylene plastic is frequently used in semiconductor and chemical industries due to its superior durability in corrosive environments.
Soft, flexible copolymer with lowtemperature toughness, and stresscrack resistance 3 hdpe easy to fabricate, durable, lightweight, low cost plastic material 5 high impact polystyrene orfitrans stiff tough plastic material that is easy to thermoform and fabricate 6 kydex thermoplastic sheet. The amount of crystalline content in the container depends on the rate of cooling. A new index test method, the notched constant tensile load nctl test, for evaluating highdensity polyethylene hdpe geomembranes regarding stresscracking resistance is presented in this paper. Wetting agents, such as detergents, accelerate stress cracking. Their outstanding chemical resistance, wide temperature range capability, and economy, position these materials for use in applications ranging from orthotic devices to chute liners, bearing pads, bushings, etc. Strain hardening modulus as a measure of environmental stress crack resistance of high density polyethylene l. High density polyethylene cope plastics abrasion resistance. The stress crack resistance of hdpe geomembrane sheet this guide was developed by the geosynthetic research institute gri with the cooperation of the member organizations for general use by the public. Environmental stress cracking is a physical phenomenon that is initiated as a slow surface crack. Standard test method for environmental stresscrack.
This is the classical location of a stresscrack failure fig. Aug 01, 2008 get a handle on stresscracking in hdpe bottles one of the first applications for blow molded hdpe bottles was the replacement of glass for bleach packaging. Besides, the number of tie molecules in this sample is less than two other ones which resulted in showing less strength under stress. A new index test method, the notched constant tensile load nctl test, for evaluating highdensity polyethylene hdpe geomembranes regarding stress cracking resistance is presented in this paper. High density polyethylene hdpe hdpe is well suited for applications where a greater tensile and compression strength is needed. Geomembrane stress cracking resistance depending on the. Moldedin stress can be another contributor to stresscracking. A guide to chemical resistance of polycarbonate sheet.
Hdpe highdensity polyethylene sheets offer excellent impact resistance, light weight, low moisture absorption, and high tensile strength. Polyethylene, including hdpe sheets, requires few natural resources to produce, generates minimal waste products, and is widely recycled. A slightly less crystalline hdpe will have better crack resistance, and density is a direct measure of crystallinity. Environmental stress cracking esc is one of the most common causes of unexpected brittle failure of thermoplastic especially amorphous polymers known at present. High density, hdpe, is produced by packing molecules more closely together. Experimental study of stress cracking in high density polyethylene pipes a thesis submitted to the faculty of drexel university by jingyu zhang. Stress cracking is defined in astm d883 as an external or internal crack in a plastic caused by tensile stresses less than its short term mechanical strength. Proteus hdpe has great chemcial resistance, impact strength, and is easily welded. Sc is a crack in a plastic caused by tensile stresses less than its shorttime mechanical strength in case.
Technical note stress crack resistance for geomembrane products. Polypropylene plastic sheets are the choice plastic for containers due to its easy manufacturability, impact resistance, and low cost. It has very high impact strength resistance and excellent processability. Hdpe technical data high density polyethylene, shore d hardness, physical properties, mechanical properties, electrical properties, thermal properties. It is important to note that escr is extremely sensitive to temperature. Slow crack resistance, often estimated by environmental stress crack resistance escr tests, is an important performance parameter for different applications of hdpe, from the blow moulding segment like bottles and containers up to the highly demanding applications like water and gas pipes. Other common plastic materials used for piping include. 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. Deblieckb amaterial development department, sabiceuropetrochemicals, research and development, oude postbaan 1, p. A materials resistance against this type of failure is called environmental stress cracking resistance escr. Consequently, the resistance of this hdpe against crack growth has been lowest.
Environmental stress crack resistance service temperatures up to 60c 140f is highly resistant to a wide variety of rather reactive cracking of escr is carried out on molded specimens 18 in. After the addition of carbon black required for uv resistance the density of the manufactured polyethylene sheet is 940 kgm3. Astm f26 18 standard test method for notched, constant. The notched constant ligament stress ncls test astm 2163 was used for the pipe liner assessment. Technical note stress crack resistance for geomembrane products the stress crack resistance scr of polyethylene pe geomembranes has been the subject of study since the introduction of the materials over 20 years ago. Cost effectiveness superior corrosion resistance high stress crack resistance moisture resistance hdpe wear and abrasion. Hitec is a high impact, high density polyethylene sheet. Hdpe s5801 is a natural colored grade produced with the latest mitsui cx slurry polymerization technology exhibiting following features. Hdpe sheets stressrelieved s r these sheets have gone through an additional annealing process to reduce stress. Dk plastics midwest plastic sheet extruder and theromformer. Because parts made with vistamaxx enhanced hdpe are tougher than those made with pure hdpe, they are less likely to fail through environmental stress cracking. Environmental stress crack resistance of polyethylene under. Hdpe 5502 is a high density polyethylene hdpe with good compromise between stiffness and environmental stress crack resistance escr.
Exxonmobil hdpe hd 8760 series high density polyethylene resin product description hd 8760 is a high density hexene copolymer designed to offer outstanding stiffness and processability. Hdpe possesses excellent impact strength and stress crack resistance in addition to chemical and corrosion resistance. These hdpe resins can be used in blowmolded bottles for everything from milk and pharmaceuticals to automotive fluids and agricultural chemicals. F2618 standard test method for notched, constant ligamentstress ncls test to determine slowcrackgrowth resistance of hdpe resins or hdpe corrugated pipe notched constant ligament stress test corrugated pipes crack growth slowcrack growth resistance plastic pipes. Environmental stress crack resistance escr testing of plastics.
Tel 610 522 drexel fax 610 5228441 geosynthetic institute. Experimental study of stress cracking in high density polyethylene. Such polyethylene sheets are known as environmental stress crack resistant grade escr grade polyethylene, and their datasheets have test values of escr performance. Hdpes are classified as either homopolymers which are stiffer, and copolymers which are more stresscrack resistant.
Stress cracking behavior of hope geomembranes and its prevention. 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. Some copolymers of ldpe are available with improved stresscrack resistance. Crackgrowth data generated on polyethylene suggests that for every 7c increase in temperature, the crackgrowth rate is doubled. Environmental stress crack resistance of polyethylene. High density polyethylene hdpe sheets grafix plastics.
Nationwides selection of ldpe sheets, rods and tubes are unmatched. Ldpe has exceptional environmental stress crack resistance properties. Pdf stress cracking resistance of hdpe geomembranes with. The fracture surfaces of stresscrack failures in igepal and in the lack of any accelerating environment are very similar see figure 3. It is well known from the pipe and cable insulation industries that pe can stress crack over long periods of time. The stress crack resistance of hdpe geomembrane sheet. It is ideally suited for the manufacture of chemical resistant products and products which come in direct contact with foodstuffs. Enhancing the environmental stress crack resistance of hdpe. One of the fastest growing plastics today is linear lowdensity polyethylene lldpe, used mainly in film applications but also suitable for injection, rotational and blow molding. It is a materials with great toughness and good mechanical strength. Slow crack resistance in polyethylene has been reported extensively in the literature 19,19. Hdpe has greater stiffness, rigidity, heat resistance, and increased resistance to permeability than ldpe. Ldpe is characterized by its good toughness and flexibility. Strain hardening modulus as a measure of environmental stress.
High density polyethylene hdpe sheet can be susceptible to a phenomenon known as environmental stress cracking esc. Stress cracking sc is an external or internal cracking in plastic induced by. Other common plastic materials used for piping include polyvinyl chloride pvc, polypropylene pp, polybutylene pb and acrylonitrilebutadienestyrene abs. 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 definition of stress cracking according to astm d883 is an external or internal crack in a plastic caused by tensile stresses less than its shortterm mechanical. The stress cracking is more severe with detergent, bleach, motor oil and some industrial chemical packaging. Hdpe boards dielectric properties and environmental stress crack resistance are also good. Impact and environmental stress crack resistance escr. Environmental stress cracking escr is the formation of cracks in a part when. The stress cracking is defined as an internal or external cracking in a plastic sheet caused by tensile stress below the short term mechanical. It is also available with a textured surface commonly used as cutting board, tradenamed sanalite. The escr of polyethylene, one of the most widely used plastic materials, is of particular concern in the plastics industry and is the subject of this investigation. Some performance evaluation tests that once took only days to run now take months with todays.
Ldpe sheets have very good formability traits and also corrosion resistant, chemical resistant and low moisture absorption. Experimental study of stress cracking in high density. High density polyethylene hdpe sheets a member of the polyolefin family, polyethylene hdpe is recognized as being extremely environmentallyfriendly. Highdensity polyethylene plastic sheet has good heat resistance and cold resistance, good chemical stability, high rigidity and toughness, and good mechanical strength. The product is classified as pe 100 and provides excellent environmental stress crack resistance properties escr combined with very good long term hydrostatic strength. Exxonmobil highdensity polyethylene hdpe resins combine toughness and stiffness with resistance to environmental stress cracking at elevated temperatures and warping. Hdpe 5502 is a pellet grade and contains antioxidants. This resin is ideally suited for applications that require the optimum balance of stiffness, processability and surface appearance.
Hdpe high density polyethylene sheet san diego plastics. Pdf stress cracking resistance of hdpe geomembranes with very. Environmental stress cracking an overview sciencedirect topics. High density polyethylene hdpe boards suppliers uhmwpe sheets. Basic understanding of stress cracking in hdpe products. Properties of lldpe are different from those of conventional ldpe and hdpe. Dielectric properties and environmental stress crack resistance are also good. Stress cracking behavior of hope geomembranes and its.
Technical note stress crack resistance for geomembrane. Escr problems get more pronounced in the summer, because of several factors related to increased heat and humidity. It is completely optional in this regard and can be superseded by other existing or new guides on the subject matter in whole or in part. The 100year stress crack resistance scr of corrugated hdpe pipes was evaluated using a 600 mm diameter pipe. Custom sizes available, call us for options and minimums. The scr tests were performed on the finished pipe at the liner and junction locations. They feature various combinations of stiffness and toughness. Strain hardening modulus as a measure of environmental. All manufacturers of hdpe geomembranes as well as resin suppliers, consultants, test organizations, owners, operators and regulators use the above recommendations, i. Hdpe, like steel, is a semicrystalline material, with no crystals in the melted state. Hdpehdpp highdensity polyethylene and highdensity polypropylene is also nontoxic and nonstaining. Environmental stress crack resistance of hdpe abg geosynthetics.
Increasing the molecular weight of the material increasing the lengths of the molecular chains can improve stress crack resistance but this. Crack resistance escr of high density polyethylene hdpe. These hdpe resins can be used in blowmolded bottles for everything from milk and pharmaceuticals to automotive fluids. Environmental stress cracking resistance of polyethylene. On this basis, bl3 has the least molecular weight and its crystallinity is higher than two other hdpe. For improved chemical resistance, please consider lexan margard mr5e polycarbonate sheet buy online at uk. Hdpe high density polyethylene typical properties hdpe sheets. It is one of the most common causes of unexpected brittle failure in thermoplastic. It has been specifically designed for the manufacture of blow molded packaging for household, industrial and cosmetics liquids.