Abstract
Ethylene vinyl acetate blends (EVA-B) (at 19 and 28 wt% vinyl acetate) were supplied by the footwear industry, along with an industrial (reference) compound labeled EVA-ref. EVA waste is an industrial sub-product crosslinked (injection sprues and unused midsoles), that was particulate through a micronization process and labeled as EVA-w. The objective of the present work was to evaluate processability and rheological parameters (using torque rheometry) when adding EVA-w to EVA-B. The EVA-w particle size distribution was bimodal, with an average diameter of 53.06 μm, and volume (%) D (10), D (50), and D (90) respectively equal to 12.47, 31.83, and 135.18 μm. However, this ample size distribution did not affect the composite mixing. FTIR-ATR analysis showed that no new crosslinking occurred after processing the composites. Low unit mixing energy (Wu), and mechanical work (as represented by ΔT values: torque stabilization temperature (Tstab)−test temperature (Ttest)) were required to mix the composites. Consequently, the dispersion of the EVA-w particles within the molten EVA-B occurred during the first 3 min of mixing, making it easier. The sensibility to shear-thinning behavior was more pronounced when adding EVA-w, especially at 25 phr. The m parameter was smaller in the composites as compared to the EVA-ref, and when adding EVA-w at 35 phr, it showed a tendency to increase. The average shear stress (\(\overline{\tau }\)) of the 15 phr composite was similar to that of the EVA-ref compound. Yet for 25 phr, a higher value was observed. The adding of EVA-w made the non-Newtonian behavior of EVA-B less pronounced. For all samples, the average viscosity (\(\overline{\upeta }\)) decreased with average shear rate (\(\overline{\dot{\gamma } }\)), revealing a pseudoplastic behavior.
Highlights
Ethylene vinyl acetate compound (EVA) is a copolymer of ethylene and vinyl acetate available with the vinyl acetate levels typically in the range 10 to 40 wt% [1, 2]
The micronized EVA waste (EVA-w) came from the twigs and unused material molded during the midsole injection (Fig. 1), both supplied by Indústria Alpargatas S/A
For EVA copolymer filled with bamboo charcoal [22], the bamboo charcoal particles size distribution and its average diameter were smaller than those of EVA-w, the rheological properties were assessed by rotational rheometry
Summary
Ethylene vinyl acetate compound (EVA) is a copolymer of ethylene and vinyl acetate available with the vinyl acetate levels typically in the range 10 to 40 wt% [1, 2]. An increasing amount of EVA waste is sent from the industrial sector to landfills, aggravating local environmental problems [10]. By reutilization this industrial new products can be obtained [11]. The high cost of managing wastes industry has led to alternative uses of EVA waste as a raw material. This, makes it possible to achieve a reduction in waste generation, economic and environmental gains as well due to sustainability manufacturing [12]
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