Reinforcement of recycled paint slag hybrid-filled lightweight calcium sulphate whisker/PVC foam composites

Lightweight crosslinked polyvinyl chloride (PVC) foam composites containing 20 wt% anhydrous calcium sulfate whiskers (CSW) were further modified with different weight ratios (5, 10, and 15 wt%) of recycled thermoplastic propenoic acid paint slag (PAPS). The effects of PAPS content were investigated regarding chemical structure, heat resistance, cellular structure, and selected properties, such as apparent density and specific compressive strength, of the resulting CSW/PVC foams. Results indicated that PAPS modified the interpenetrating polymer network (semi-IPN) by adjusting the relative ratios of cyano groups, urea, biuret, and amide linkages. The trend in the foams' thermal properties showed an inflection point at 10 wt% PAPS content. In this case, compared with a CSW/PVC sample without PAPS, the PAPS foams exhibited increasing degradation temperature from 389.3 to 416.2 °C, with a 50% weight loss and glass transition temperature (Tg) increasing from 70.9 to 79.6 °C. Moreover, the use of PAPS produced small and homogeneous cellular structures, providing greater foam stiffness. Although PAPS addition resulted in foams of higher density, a 0.6-3.5-fold improvement in specific compressive strength, compared to foam without PAPS, was observed.