Ethylene-propylene binary copolymers rubbers

Three characteristics of ethylene-propylene binary copolymer rubbers (EPM rubbers) are of interest ... 

More homogeneous copolymer cpmpositions are obtained with soluble Zieg-ler-Natta catalysts, especially where monomer compositions are maintained relatively constant during polymerization. Commercially important ethylene-propylene binary copolymers (EPM rubbers) and ethylene-propylene-diene ternary copolymers (EPDM rubbers) are made by this process. 

Random copolymer addition to binary blends involving copolymers with structural units equal or similar to the blend components or with specific interacting groups capable of non-reactive interaction with one of both the blend components comprises another ternary polymer addition approach. An early example involved EPR (ethylene-propylene rubber) addition to HDPE/PP blends, where synergistic impact strength was observed. In some cases, the random copolymers have been compared to block copolymers comprised of the same units. The compatibihzation of LLDPE/PMMA and LLDPE/poly(MMA-co-4-vinyl pyri-dine(4VP)) blends with poly(ethylene-co-methacrylic acid) (EMAA) addition were compared [47]. Modest improvements in LLDPE/PMMA dispersion and strength were observed. The specific acid-base interaction allowed for much larger improvements with EMAA addition to LLDPE/PMMA-CO-4VP blends. 

C02-assisted viscosity reduction has been observed for the following polymer systems PMMA [82], polypropylene [82], poly(vinylidene fluoride) [82], poly(di-methylsUoxane) [1, 85, 87, 90, 91], poly(ethylene glycol) [92-96], poly(ethylene glycol) nonphenyl ether [97], acronitrile copolymer (65 wt% AN) [89], polyamide 11 [48], low-density polyethylene (LDPE) [82, 98], poly(propylene glycol) and suspensions of fumed sihca in poly(propylene glycol) [86], polystyrene [80, 81, 99], binary mixtures of polystyrene and toluene [84, 100, 101], and biomaterials [101]. Viscosity reduction has also been observed for the following blends polyethylene and polystyrene [79, 102], polystyrene and PMMA [103], PMMA/rabber and polystyrene/rubber [104]. 

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