Synergistic effects of organosilicon flame retardant and DOPO-based reactive compatibilizer for high performance PC/PBT composites

Abstract

PC/PBT alloy is flammable resulting in fire safety hazards in practical applications and the existing flame retardants have a great influence on the mechanical properties, which limits its application range. Therefore, it is an urgent problem to improve the flame retardancy of PC/PBT alloy while taking its mechanical properties into account. Herein, a novel flame retardant and reactive compatibilizer was synthesized by grafting 9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide (DOPO) onto ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA), named as DOPO-EG, to improve the flame retardancy and mechanical properties of PC/PBT alloy simultaneously. Additionally, based on the effective synergistic effect of enhancing the charring and flame retardancy between silicon and phosphorus, the organosilicon flame retardant (RMSi) is introduced and compounded with DOPO-EG to prepare excellent flame retardancy PC/PBT/DOPO-EG/RMSi composites. The results showed that the PC/PBT/DOPO-EG/RMSi composites with 10 wt% DOPO-EG and 8 wt% RMSi (CBE10P10Si8) reached UL-94 V-0 rating and the peak of heat release rate (PHRR) and total heat release rate (THR) of CBE10P10Si8 decreased by 42% and 16% respectively. This is due to the fact that DOPO is cracked into phosphorus radicals to capture and eliminate the active H and OH radicals, inhibiting the chain free radical reaction, and RMSi is enriched on the surface of CBE10P10Si8 to form an inorganic oxygen insulation protective layer during combustion. The impact strength of CBE10P10Si8 increased from 5.8 kJ/m2 to 11.9 kJ/m2. The improvement of impact strength is owing to the existence of DOPO-EG which promotes the formation of the interface layer between PC and PBT phases, resulting in the transfer of stress between the two phases. This work provides a new method for the preparation of PC/PBT alloy with excellent flame retardancy and mechanical properties, and also provides a certain reference value for the research of flame retardancy and toughening modification of polymer composites.