Performance-Optimized Polyvinyl Chloride Composites: Balanced Flame Retardancy, Smoke Suppression, Strength and Low-Temperature Resistance

This work aimed to improve both mechanical properties and flame retardancy in polyvinyl chloride (PVC)/hydrogenated nitrile-butadiene rubber (HNBR) thermoplastic elastomer composites through the melt blending technique. To achieve this, semi-reinforced furnace black (SRF) was blended with HNBR as a reinforcing agent. Meanwhile magnesium hydroxide (MH) and antimony trioxide, acting as flame retardants, were incorporated into plasticized PVC. Mechanical, combustion, and differential scanning calorimetry (DSC) tests were conducted to evaluate the effects of MH and SRF. Results show that incorporating 10–30 phr SRF in HNBR and 100–150 phr MH in PVC has led to composites with significantly improved properties, including an enhanced limiting oxygen index (36.2%), reduced smoke density rate (11.8%), and lowered maximum smoke density (28.7%). Tensile strength improved to 9.32 MPa, while elongation at break remained at 317%. DSC analysis revealed a glass transition temperature of −23.5°C, indicating excellent low-temperature resistance. These PVC/HNBR composites are suitable for applications in wires, cables, automotive parts, building seals, and low-temperature industrial products.