Synergistic flame retardant effect of poly(ether sulfones) and polysiloxane on polycarbonate

Flame retardance of bisphenol A polycarbonate (PC) was improved by the co‐addition of poly (ether sulfones) (PES) and polysiloxane/acrylate copolymer (PSiA) while retaining a high rigidity and toughness. A UL 94 V‐0 rating for 1.6‐mm thick samples of PC/PES/PSiA blend with 10.0 wt % PES and 0.5 wt % PSiA (PC/10PES/0.5PSiA) was obtained. Its average heat release rate (av‐HRR) in a cone calorimeter measurement was decreased by 19% on the basis of PC/PES blend with 10.0 wt % PES. Scanning electron microscopy (SEM) morphologies of impact‐fractured surfaces revealed that the incorporation of 0.5 wt % PSiA decreased the dimensions of PES dispersed phase and provoked the uniform distribution of PES in PC matrix. Thermogravimetric‐Fourier transform infrared spectroscopy analysis results revealed that PSiA dominantly promoted the degradation of PC and the degraded products were combined with PES to form a superior flame‐retarded carbon layer. A higher sulfur and silicon content on the residue surface after vertical burning tests detected by SEM/energy dispersive spectrometer signified their accumulation during combustion.