During dynamic vulcanization of polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM) blends with dicumyl peroxide/triallyl cyanurate, there is a possibility of the generation of in situ graft links at the interface. Three potential compatibilizers (PP-grafted EPDM, styrene-ethylenebutylene-styrene, and trans-polyoctenamer) for PP/EPDM blends were first investigated as references to obtain a quantified insight into the effects to be expected from in situ graft links. Only the first compatibilizer showed some compatibilizing action in straight, unvulcanized blends, as evidenced by a slight increase in the tensile strength of the blend and a somewhat smaller EPDM particle size within the PP matrix. Also, dynamic mechanical testing, in particular, the glass-transition temperatures of the PP and EPDM components, showed some signs of compatibilization. The PP-grafted EPDM resembled most closely the structures of PP and EPDM. In the spectra obtained with high temperature, solid-state NMR, there was an indication that PP-EPDM graft links were generated during the dynamic vulcanization process that still remained after the extraction of the free PP phase from the thermoplastic vulcanizate film. NMR relaxation experiments gave further evidence for the graft links formed in situ. In all cases, only qualitative indications could be achieved because of the extremely low number of graft links formed.
- Graft copolymers