Using solid waste from the leather tanning industry to produce a mixed calcium/zinc thermal stabilizer for polyvinyl chloride

Abstract

The leather tanning industry has historically posed considerable environmental challenges owing to the substantial solid waste it produces. This study examines innovative uses for the solid waste generated by this sector, focusing on the waste from the fleshing process. Our research involved extracting fat from fleshing waste, synthesizing Ca and Zn carboxylates from the extracted fat, and assessing their effectiveness as a combined Ca/Zn thermal stabilizer for polyvinyl chloride (PVC). The synthesized Ca and Zn carboxylates contained 6.4% Ca and 11.4% Zn, respectively, while the total fatty matter was determined to be 86.2% and 88.5%, respectively. Thermal analysis indicated that both carboxylates remained stable up to 200 °C. Tests on dehydrochlorination and roll milling revealed that the mixed Ca/Zn thermal stabilizer effectively improved the thermal stability of PVC resin. It also showed a synergistic effect when combined with pentaerythritol, enhancing its overall efficacy. The synthesized mixed Ca/Zn thermal stabilizer exhibited thermal stabilizing properties and flowability comparable to those of mixed Ca/Zn stearate, a widely used thermal stabilizer for PVC. These results suggest that fleshing fat could serve as a valuable raw material in the production of mixed Ca/Zn-based PVC thermal stabilizers.