The Effect of a Copolymer of Ethylene and Vinyl Acetate on the Formation of the Structure and the Processing Properties of Olefinic Thermoplastic Elastomers

Abstract

Optical microscopy and dielectric relaxation spectroscopy (DRS) were used to study the structure of dynamically vulcanised mixes based on polypropylene, ethylenepropylenediene rubber, and copolymers of ethylene and vinyl acetate (Levapren 400, 600, 700). For the microscopic investigations, we used a complex consisting of a Leica DM-2500 optical microscope, a DFC 420C cooling chamber, and a special computer desk. DRS data were obtained on a BDS 89 instrument (NovoControl) at temperatures ranging from −150 to +100°C at a heating rate of 2°C/min and a frequency of 110 Hz. The influence of the content of Levapren and the proportion of vinyl acetate in its composition on the morphology and processing properties of olefinic thermoplastic vulcanisates (TPVs) was investigated. The combination of the discovered changes in the fine structure and DRS data indicate the preferential interaction of Levapren with the rubber component. The evolution of the morphology of the TPVs with increase in the volume fraction of vinyl acetate is not monotonic, which is consistent with the nature of change in the physicomechanical properties of the TPVs. Combined analysis of the morphological characteristics and processing properties of TPVs showed that, to achieve high values of the deformation and strength properties, a uniform distribution and high polydispersity of the ingredients are necessary. Increase in the elastic properties of the material is ensured by modification of the polypropylene phase to form fibrillar structures, while the flow of TPEs that is necessary for processing is facilitated by modification of the rubber phase.