Abstract
This study aims to investigate a recycling alternative for a crosslinked ethylene-vinyl acetate (EVA-c) copolymer (75 wt% of gel content) from the shoe industry through mixing with virgin and recycled polyethylenes. The Drais equipment, an ultra-high-speed thermo-kinetic mixing and compounding system specifically developed for very difficult compounding, mixing and dispersion applications, was chosen for processing highly loaded EVA-c (60-90 wt%) compounds. PE/ EVA-c mixtures presented additive or synergistic mechanical properties, which reveals good compatibility between the polymers. The addition of dicumyl peroxide (DCP) as a crosslinking agent was also evaluated. The PE/EVA-c/DCP mechanical properties were found to be influenced by the degree of crosslinking; significant softening was observed for mixtures with DCP contents higher than 2 phr, that is, with maximum gel content. It is proposed here that the softening caused by DCP addition was related to a decrease in the degree of crystallinity; although the crosslinking process itself make polymeric materials more rigid, for semicrystalline polymers it causes defects in their crystalline arrangement, increasing the volume of amorphous phase, i.e., the crosslinking process induces a decrease in the degree of crystallinity of PE/EVA-c mixture, presenting a rubber-like behavior. Therefore, the use of the recycling procedure developed in this work represents an alternative for crosslinked EVA-c and PE re-use through a low-cost and easy-to-handle batch mixer (Drais), making it possible to prepare materials with a range of mechanical properties suitable for technological applications.
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