PP-EPDM thermoplastic vulcanisates (TPVs) by electron induced reactive processing

Reactive processing combines melt mixing process and chemical reaction simultaneously. TPVs are produced by such reactive processing. Polymer modification with high energy electrons is based on generation of excited atoms or molecules and ions for subsequent molecular changes via radical induced chemical reactions. In the present study, electron induced reactive processing is used for the development of TPVs. A 1.5 MeV electron accelerator was directly coupled to an internal mixer in order to induce chemical reactions by energy input via high energy electrons under dynamic conditions of melt mixing of polypropylene (PP) and ethylene propylene diene monomer rubber (EPDM). The influence of absorbed dose (25 to 100 kGy) as well as electron energy (1.5 and 0.6 MeV) and electron treatment time (15 to 60 s) have been studied. Increased values of both tensile strength and elongation at break of the TPVs indicate in-situ compatibilisation of PP and EPDM as well as cross-linking in the EPDM phase upon electron induced reactive processing. Dynamic mechanical analyses showed a decrease in value of glass transition temperature peak of EPDM in tangent delta curve with increasing dose. This also indicates higher degree of cross-linking in EPDM phase, which is further supported by a gel content that is higher than the EPDM content itself in the blend.