Enhancement of notched impact strength and flame retardancy in polycarbonate via micro-crosslinked polysiloxane

Polycarbonate (PC) is a crucial engineering thermoplastic, but its impact strength is highly sensitive to notches, with even minor ones leading to significant reductions in mechanical performance. In this work, a crosslinked polysiloxane (VMQ) was synthesized and incorporated into PC to enhance both its toughness and flame retardancy. The introduction of VMQ greatly improved the notched impact strength and flame retardancy of PC. The addition of 5 wt% VMQ significantly enhanced the notched impact strength from 8.8 to 75.4 kJ/m², representing an improvement of 756.8 %. Furthermore, the elongation at break and tensile toughness increased by 61.2 % and 46.5 %, respectively. Notably, even at −10 °C, the enhanced notched impact strength was almost fully retained. Additionally, the PC/5%VMQ composite achieved a UL-94 V-0 rating, with a limiting oxygen index (LOI) of 28.7 %, a 38.2 % reduction in peak heat release rate (PHRR), and a 13.9 % decrease in total smoke production (TSP). The toughening and flame-retardant mechanisms of VMQ were thoroughly investigated. This work provides an innovative approach to simultaneously improve the flame retardancy and toughness of PC.