Study On Dynamically Vulcanized PP/EPDM/ZDMA(MDMA) Composites

Studies on polypropylene/ethylene-propylene-diene (PP/EPDM) composites have beencarried out extensively and systematically for decades, and various views have been proposedto explain its excellent properties. It is found that the compatibility and interface adhesionhave great influence on properties for PP/EPDM blends. Zinc dimethacrylate (ZDMA) andmagnesium dimethacrylate (MDMA) are good reinforcing fillers for rubbers, and there existsreactive groups on molecule chains, which can polymerize to form homopolymers (h-PZDMAor h-PMDMA) or graft onto rubber chains to form graft products (g-PZDMA or g-PMDMA),which can act as better reinforcing fillers for rubber.We prepared PP/EPDM/ZDMA (MDMA) composites via melt mixing by introducedZDMA (MDMA) into peroxide induced dynamically vulcanized PP/EPDM composites in thiswork. ZDMA (MDMA) play role of in situ compatibillization for PP/EPDM blends on theone hand, and reinforce EPDM phase on the other hand. The morphologies, structure andproperties of the dynamically vulcanized PP/EPDM/ZDMA (MDMA) composites werestudied.In the presence of peroxide radicals, ZDMA was polymerized to form nano h-PZDMAand dispersed in PP/EPDM blends. On the other hand, it was grafted onto PP or EPDMmolecule chains, which improved interface adhesion between PP and EPDM phases, thus playrole of in situ compatibilization for PP and EPDM. The addition of ZDMA could restrain thedecomposition of PP at the same time. The study on mechanical properties ofPP/EPDM/ZDMA composites showed that with increasing EPDM content, the impactstrength increased gradually, while tensile strength, tear strength and hardness decreased,strain at break increased at first and then decreased. The analysis of SEM morphologyindicateed the existence of “sea-island” structure in which the crosslinked EPDM particlesdispersed in continuous PP matrix (EPDM content no more than80%). Moreover, withincreasing ZDMA concentration, the size of crosslinked EPDM particles decreased, and themixing torque, tensile strength, impact strength, strain at break and viscosity increased.Particularly, the impact strength increased from30.2kJ/m2without ZDMA to58kJ/m2whenZDMA concentration was30%of EPDM with PP/EPDM=80/20. With increaseing ZDMA concentration, the crystallization temperature of PP was improved, while too much ZDMAconcentration seemed to have a negative effect on crystallinity of PP phase.The study on non-isothermal crystallization kinetics of PP/EPDM/MDMA systemindicateed the h-PMDMA particles formed in the presence of peroxide free radicals acted asheterogeneous nucleation, which improved the crystallization temperature and decreased thespherulite size of PP phase. The Avrami and Mo’s models well described the non-isothermalcrystallization kinetics. However, the Ozawa model was not suitable for the system. Moreover,the study on crystallization activation energy (ΔE) showed that ΔE increased with dynamicvulcanization and the addition of MDMA.