Effects of mixing sequence on peroxide cured polypropylene (PP)/ethylene octene copolymer (EOC) thermoplastic vulcanizates (TPVs). Part. I. Morphological, mechanical and thermal properties

The effects of mixing sequence on the mechanical, morphological and thermal properties of polypropylene (PP)/ethylene octene copolymer (EOC) TPVs were studied. Three different mixing sequences were employed. They are as follows: (a) preblending method—melt mixing of PP and EOC followed by dynamic vulcanization (b) phase mixing method—curative master batch of EOC added in molten PP (c) split addition method—preblending procedure followed by addition of half part of PP (dilution of dynamic vulcanizate). Results indicate that mechanical and morphological characteristics are strongly influenced by the mixing sequence. Phase mixing method exhibits better mechanical and morphological characteristics. The best balance of properties was observed at 3 milliequivalents (2 phr) concentration of peroxide. Tensile failure surface analyses of the TPVs prepared have been employed to gain an insight into the mechanism of failure and to correlate the mechanical properties. Thermal characterization of the uncrosslinked and dynamically crosslinked blends was performed to understand the microstructural changes obtained.