Enhanced Fire‐Safe and Mechanical Properties of Polyvinyl Chloride Composites via Surface‐Modified Magnesium Hydroxide and Processing Optimization

ABSTRACT This work aimed to enhance the flame retardancy, smoke suppression, and mechanical properties of a low‐temperature‐resistant plasticized polyvinyl chloride/hydrogenated nitrile‐butadiene rubber (PVC/HNBR) multifunctional composite. Magnesium hydroxide (MH) filler was modified via dry surface treatment using stearic acid, titanate coupling agent, or silane coupling agent (SC). The modified MH was incorporated into PVC/HNBR via two methods to investigate the composite's combustion behavior, mechanical properties, and low‐temperature resistance. Results demonstrated that the composite prepared by first blending SC‐modified MH with HNBR, followed by mixing with plasticized PVC, exhibited optimal overall performance. This PVC/HNBR composite achieved a limiting oxygen index of 33.9%, a smoke density rating of 26.21%, a tensile strength of 11.30 MPa, an elongation at break of 415%, and a glass transition temperature as low as −23.2°C. Scanning electron microscopy was used to analyze MH dispersion within the matrix, correlating it with the macroscopic properties. This study offers an effective approach for selecting MH modifiers and developing high‐performance flame‐retardant and cold‐resistant materials.