Thermal stability of plasticized poly(vinyl chloride) compounds stabilized with pre-heated mixtures of calcium and/or zinc stearates

Processing and post-processing thermal stability of poly(vinyl chloride) compounds, plasticized with di(ethyl hexyl) phthalate (DEHP) and epoxidized soybean oil (ESO), using several ratios of calcium/zinc stearates are reported here. Two series of compounds were prepared, varying the DEHP or ESO concentrations. The compounds were prepared as follows: (1) preheating stearates, (2) dry-blending the compound components, (3) pelletizing the dry-blend and (4) extruding the pellets to obtain a ribbon geometry. Processing thermal stability was determined by: (a) mechanical characterization and (b) visual color comparison of samples. Post-processing thermal stability was followed by: (a) measurement of HCl release from heated pellets and (b) color changes in heated ribbon samples. Thermal stability was improved by the presence of DEHP and ESO. In addition, improved color stability was achieved with intermediate CaSt2/ZnSt2 ratios, and minimal HCl release was achieved in formulations without ZnSt2. Results can be directly applied to design a formulation for a specific application.