Flammability Performance of Ceramifiable Polydimethylsiloxane (PDMS) Composites With Needle-Like Wollastonite

Abstract

Ceramifiable flame retardant polydimethylsiloxane (PDMS) composites were successfully fabricated using solution blending and hot pressing, incorporating needle-like wollastonite (WT), zinc borate (ZB), aluminum hydroxide (ATH), and glass powder (GP) as fillers. The thermal, mechanical, and flame retardant properties, along with the ceramization behavior of the composites, were thoroughly characterized. The findings demonstrate that WT is more effective than conventional lamellar mica in enhancing both tensile strength and flame retardancy, as well as promoting ceramization. The optimized PDMS/WT/ZB/ATH/GP system passed the UL-94V-0 rating and exhibited an increased limiting oxygen index (LOI) of 28.5%. Cone calorimetry results indicated that WT effectively reduced the peak heat release rate and delayed ignition of the composites. The flame retardant mechanism is mainly attributed to the WT with a high aspect ratio, which serves as a sintering aid, accelerates the eutectic reaction, and promotes the formation of a ceramic barrier at lower temperatures by reducing the resistance to liquid-phase migration.