3.5 Ethylene-propylene Rubber (EPDM), Polyisobutylene (Butyl) Rubber and Relative Low Molecular Weight EPR, PIB and PAO Materials The aliphatic hydrocarbon polymers are soft in nature due to very weak interpolymer interaction. The prevention of polymer chain crystallization by incorporating comonomer units can result in the material with elastic properties with low Tg. * EPR and EPDM EPDMEPRZiegler-Natta or MetallocenecatalystCH3++DieneCH2=CHCH2=CH2x: 50-60% y: 35-45%z: 1 -8%CH3CH5-ethylidene-2-norbornene (ENB)CH3CHCHCH2CH2=CHDienes: 1,4 hexadeien zyyxxCH3CH3-(CH2-CH2) -(CH2-CH) - -(CH2-CH2) -(CH2-CH) -(diene) -At the present time, these materials are prepared exclusively by transition metal (Ziegler-Natta and metallocene) coordination polymerization. Generally, the solution processes are preferred in which a soluble catalyst system is used and the polymer remains in solution rather than form a slurry. A common
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