Polypropylene diene block copolymers

The styrene-diene-styrene triblock copolymers are not used extensively in traditional rubber applications because they show a high level of creep. The block copolymers can, however, be blended with many conventional thermoplastics such as polystyrene, polyethylene, and polypropylene, to obtain improved properties. A major area of use is in footwear, where blends of SBS and polystyrene have been used with remarkable success for crepe soles. 

The polyallomers constitute the class of block copolymers where both components are capable of crystallizing independently (Coover et al, 1966 Hagenmeyer and Edwards, 1966, 1970 Eastman Chemical Products, n.d.). The most important member of this family contains crystalline, stereoregular polypropylene as the major component and polyethylene as the minor component. As expected for a block copolymer, these products differ greatly in behavior from mechanical blends of polyethylene and polypropylene, and also from their random copolymers, poly(propylene-co-ethylene). When crosslinked with a diene monomer, the latter copolymers are known as EPDM rubbers (Lee et a/., 1966 Rodriguez, 1970, Chapter 13), while the former blends are of apparently little interest. In Figure 6.28 and 6.29 the... 

An elastomer which upon heating turns into regularly behaving linear polymer. Polystyrene-polybutadiene block copolymers, polypropylene blends with ethylene-propylene-diene terpolymer provide examples. 

Interfacially active graft or block copolymers of the t5 pe A-B or A-C may compatibilize the immiscible polymers A and B provided that C is also miscible or capable of strong interactions with B. Poly(ethylene-co-propylene) elastomer (EPR) or poly(ethylene-co-propylene-co-diene) (EPDM) is an example of such nonreactive compatibilizer for polyethylene/polypropylene (PE/PP) blends. 

Electrical properties have been reported on numerous carbon fiber-reinforced polymers, including carbon nanoflber-modified thermotropic liquid crystalline polymers [53], low-density polyethylene [54], ethylene vinyl acetate [55], wire coating varnishes [56], polydimethyl siloxane polypyrrole composites [50], polyacrylonitrile [59], polycarbonate [58], polyacrylonitrile-polycarbonate composites [58], modified chrome polymers [59], lithium trifluoromethane sulfonamide-doped polystyrene-block copolymer [60], boron-containing polyvinyl alcohols [71], lanthanum tetrafluoride complexed ethylene oxide [151, 72, 73], polycarbonate-acrylonitrile diene [44], polyethylene deoxythiophe-nel, blends of polystyrene sulfonate, polyvinyl chloride and polyethylene oxide [43], poly-pyrrole [61], polypyrrole-polypropylene-montmorillonite composites [62], polydimethyl siloxane-polypyrrole composites [63], polyaniline [46], epoxy resin-polyaniline dodecyl benzene sulfonic acid blends [64], and polyaniline-polyamide 6 composites [49]. 

Melt blending of polymers is a widely used technique for tailor-making polymeric materials to generate the desired properties. Blending polypropylene block copolymer (PPBC) with elastomeric ethylene-propylene-diene terpolymer (EPDM) produces a range of useful materials commercialized in early 1970 s that found significant uses in the automotive industry. Polyolefin-based bumpers dominate the automobile market in Europe and Japan and have made in-roads in the North American market. In India, the polyolefin blend for car bumpers was commercialized in 1992. 

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