RELATIONSHIP BETWEEN STRAIN-RATE, TEMPERATURE, AND IMPACT FAILURE-MECHANISM FOR POLY(VINYL CHLORIDE) AND POLY(ETHYLENE-TEREPHTHALATE)

One approach to the purification of recycled thermoplastic mixtures is selective grinding to induce differences in sizes and shapes between polymers with different; compositions. These mixtures can then be sepa rated using one of several technologies including conventional sieving or hydrocyclones. Recycled poly(vinyl chloride) and poly(ethylene ter ephthalate) often are cross-contaminated with each other since they ha ve overlapping density ranges and are very difficult to separate using methods such as flotation. Selective grinding followed by physical se paration might be a preferred method for separating such a polymer pai r if processing ''windows'' for inducing differences in failure mechan isms can be found. There is a temperature range over which PET fails i n a ductile mode while PVC fails in a brittle mode for impact grinding experiments. This range is not accurately predicted by failure mechan ism and beta-transition temperature diagrams.