Multifunctional peroxides as a means to improve properties of dynamically vulcanized PP/EPDM blends

Thermoplastic elastomers produced by simultaneous mixing and crosslinking of a rubber and a thermoplastic are commonly called thermoplastic vulcanizates (TPVs) or dynamic vulcanizates. Our earlier work has demonstrated that the application of a proper peroxide in combination with a suitable classical co-agent provides a good overall balance of physical properties in PP/ EPDM TPVs. Commonly used peroxides produce more or less volatile decomposition products, which sometimes possess a typical smell or show a blooming effect or voids formation. Multifunctional peroxides were developed to reduce those problems. They combine peroxide and co-agent-functionality (reactive unsaturated groups) in a single molecule. The main objectives of the present work are to show the effects of special kinds of multifunctional peroxides as curing agents on the properties of PP/EPDM TPVs at a fixed blend ratio and to avoid the formation of unpleasant byproducts. The multifunctional ones exhibit more or less comparable properties as co-agent assisted commonly used peroxides. This article focuses on understanding the phenomena in terms of mechanistic and kinetic aspects of the peroxides.