Low-temperature toughness

By altering theses variables, blends may be produced to give products varying in processability, toughness, low-temperature toughness and heat resistance. 

Ethylene Acrylic Rubber Copolymers of ethylene and acrylic esters. Has good toughness, low temperature properties, and resistance to heat, oil, and water. Used in auto and heavy equipment parts. 

Polyurethanes in general are noted for their abrasion resistance, toughness, low-temperature impact strength, cut resistance, weather resistance, and fungus resistance. Specialty polyurethanes include glass-reinforced products, fire-retardant grades, and UV-stabilized grades. 

Properties Stiffness Toughness Low-temperature ductUity Stiffness... 

Polypropylene-EPDM or EPR combinations are the most important [13,14] and are used to make products such as injection-molded bumpers for automobiles, where a combination of toughness, low temperature flexibility, and low cost makes them... 

Although not as resistant as cellulose esters to acids, it is much more resistant to bases. An outstanding feature is its toughness at low temperatures. 

High strength, low alloy (HSLA) steels often contain 0.10—0.30% molybdenum. These steels exhibit toughness at low temperatures and good weldabiHty. They are used extensively for undersea pipelines (qv) transporting gas and oil from offshore weUs to pumping stations on shore, and are also used extensively in remote Arctic environments. 

Film. By far the largest appHcation for LLDPE resins (over 60% in the United States) is film. Because LLDPE film has high tensile strength and puncture resistance, it is able to compete with HDPE film for many uses. The toughness and low temperature properties of LLDPE film also exceed those of conventional LDPE. Furthermore, because LLDPE resins exhibit relatively low strain hardening in the molten state and lower extensional viscosity, it can be produced at high rates with Httle risk of bubble breaks. 

Polypropylene polymers are typically modified with ethylene to obtain desirable properties for specific applications. Specifically, ethylene—propylene mbbers are introduced as a discrete phase in heterophasic copolymers to improve toughness and low temperature impact resistance (see Elastomers, ETHYLENE-PROPYLENE rubber). This is done by sequential polymerisation of homopolymer polypropylene and ethylene—propylene mbber in a multistage reactor process or by the extmsion compounding of ethylene—propylene mbber with a homopolymer. Addition of high density polyethylene, by polymerisation or compounding, is sometimes used to reduce stress whitening. In all cases, a superior balance of properties is obtained when the sise of the discrete mbber phase is approximately one micrometer. Examples of these polymers and their properties are shown in Table 2. Mineral fillers, such as talc or calcium carbonate, can be added to polypropylene to increase stiffness and high temperature properties, as shown in Table 3. 

Polypropylene. PP is a versatile polymer, use of which continues to grow rapidly because of its excellent performance characteristics and improvements in its production economics, eg, through new high efficiency catalysts for gas-phase processes. New PP-blend formulations exhibit improved toughness, particularly at low temperatures. PP has been blended mechanically with various elastomers from a time early in its commercialisation to reduce low temperature brittleness. 

ABS can be blended with bisphenol A polycarbonate resins to make a material having excellent low temperature toughness. The most important apphcation of this blend is for automotive body panels. 

At very high and very low temperatures, material selection becomes an important design issue. At low temperatures, the material must have sufficient toughness to preclude transition of the tank material to a brittle state. At high temperatures, corrosion is accelerated, and thermal expansion and thermal stresses of the material occur. 

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