SOME ASPECTS OF ISOTACTIC POLYPROPYLENE CRYSTALLIZATION IN AN ETHYLENE-PROPYLENE-DIENE RUBBER MATRIX

Crystallization of isotactic polypropylene (iPP) in an ethylene-propyl ene-diene rubber matrix (EPDM), crosslinked with dicumyl peroxide (DCP ), has been studied. A discrepancy concerning the degree of crystallin ity of the blends determined using different experimental techniques, has been discovered and an effort to explain it is made. iPP was found to recrystallize in EPDM in a manner, depending on the amount of plas tomer added. Nucleation, being predominantly homogeneous for 'pure' iP P, becomes predominantly heterogeneous for its blends with EPDM. The s maller the polypropylene content the more a defect crystalline phase i s formed. The defects, as well as an orientation were shown to be resp onsible for the higher, in comparison with other methods, degree of cr ystallinity determined by wide-angle X-ray scattering.