Low Temperature Impact Strength

Some cast (unoriented) polypropylene film is produced. Its clarity and heat sealabiUty make it ideal for textile packaging and overwrap. The use of copolymers with ethylene improves low temperature impact, which is the primary problem with unoriented PP film. Orientation improves the clarity and stiffness of polypropylene film, and dramatically increases low temperature impact strength. BOPP film, however, is not readily heat-sealed and so is coextmded or coated with resins with lower melting points than the polypropylene shrinkage temperature. These layers may also provide improved barrier properties. 

The low temperature impact strength of stmctural steels was found to be significantly improved with the additions of 0.022—0.008% Te. The low (—40° C) temperature impact strength of a steel annealed at blue brittie temperature of 350°C did not show any embrittlement effect with the addition of. 002% Te (76). 

In these mbber-modified polystyrene polymers, the mbbers should have low T, large particle sizes (0.5—5 J.m), graftable and cross-linkable sites, and should be compatible with styrene monomer (93). Polybutadiene, with a T of —SS C, meets all of these requirements and is used most frequently. These mbber-modified systems exhibit excellent low temperature impact strength, a required attribute for use in refrigerators. 

This daia indicates that the random copolymer has greater transparency but inferior low temperature impact strength. 

Leisure Flotation devices Marine buoys Sailboards Toys Canoes/kayaks Low temperature, impact strength cost, weatherability Low temperature, impact strength cost, weatherability Low temperature, impact strength cost, weatherability Low temperature, impact strength cost, weatherability Low temperature, impact strength cost, weatherability... 

Industrial Tool boxes, ice chests Trash containers, drums Hot-water tanks Low temperature, impact strength, cost Low temperature, impact strength, cost Low temperature, impact strength, cost... 

The coverage of the filler with an elastomer layer has been studied mostly in PP composites, but occasionally in other polymers as well. PP has a poor low temperature impact strength, which is frequently improved by the introduction of elastomers [107]. Improvement in impact strength, however, is accompanied by a simultaneous decrease of modulus, which cannot be accepted in certain applications a filler or reinforcement is added to compensate the effect. Although most of the papers dealing with these materials agree that the simultaneous introduction of the two different types of material (elastomer, filler) is beneficial. 

Some of these block copolymers have improved low temperature impact strength and higher stress-crack resistance than neat BPA polycarbonate Blends. The concept of blending two or more commercially available materials to create a new material having properties different from either starting material has generated a great deal of interest. Polycarbonate blends are used to tailor performance and price to specific markets. 

An important corollary to impact behavior of reinforced thermoplastics is shown in Figure 6. Two different ABS resins are used for this illustration relating to low temperature impact strength retention. The unreinforced ABS will retain from 20-30% of its room temperature impact strength in going to — 20°F. The graphs for both the low and high... 

The most important commercial blends of BPA-PC are poly(acrylonitrile-butadiene-styrene) (PC/ABS) and polybutylene terephthalate (PC/PBT) or polyethylene terephthalate (PET). Commercial grades of PC/ABS include CYCOLOY (GE), Bayblend (Bayer), and PULSE (Dow). PC/ABS blends exhibit improved flow and processability and enhanced low-temperature impact strength in comparison to PC (Fig. 3). These blends are widely used in applications requiring enhanced impact resistance, such as interior automotive parts and computer and electronics applications such as computer housings and cell phones. Non-halogenated flame-retardant PC/ABS blends are widely available. Poly(acrylic-styrene-acrylonitrile) (PC/ ASA) blends (GELOY , GE Luran , BASF) provide improved weatherability for outdoor applications such as exterior automotive parts, but exhibit reduced impact performance at low temperatures in comparison to PC/ABS. PC/PBT or PET blends (XENOY , GE Makroblend , Bayer) provide enhanced chemical resistance and weatherability for applications such as lawn and garden equipment and automotive bumpers and fasdas. 

PE/Elastomer Blends Polyolefins have been modified by the incorporation of elastomers to improve low temperature impact strength and elongation. Table 1.39 provides examples of these systems. 

PE has been used to improve the low temperature impact strength of PP (see Table 1.41). The blends are mostly immiscible, compatibilized either by addition of EPR, EPDM, by reactive blending, or by post-blending co-crosslinking, e.g., by electron beam or j radiation [Utracki and Dumoulin,... 

PE/PP compatibilized with PIB low temperature impact strength Lehane, 1964... 

Isotactic PP with sPP low temperature impact strength Emrick, 1966... 

PE and PP EPR good flow properties and a very good low temperature impact strength. Schreck etal., 1994... 

PC/ABS blends can withstand temperatures as low as minus 40°C, and the abuses associated with recreational skiing. Snowmobile throttle and brake handles are fabricated from PA/ABS alloy to take advantage of the material s gasoline resistance combined with low temperature impact strength about equal to PC. ASA is coextruded with ABS/PC blend for pleasure boat hulls. 

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