Improving the fracture toughness, flame retardancy and smoke suppression of ABS by core-shell elastic flame retardant particles with P/Si synergistic effect

• Elastic particles ADP@SiR with P/Si and core-shell structures are prepared. • Shell structure improves interaction between matrix and the fillers remarkably. • ADP@SiR achieved good balance in fire-safety and mechanical properties. • ADP@SiR accelerates the pyrolysis of ADP and exerts superior quenching effect. Acrylonitrile-butadiene-styrene copolymer (ABS) is widely used in structural parts owing to its impressive mechanical properties. However, a delicate balance between flame retardancy and mechanical properties is essential for the safety performance of flame retardant ABS. To address this concern, elastic particles (ADP@SiR) were constructed by using silicone rubber (SiR) and aluminium diethyl hypophosphite (ADP). On the one hand, the core-shell structure realized effective isolation of flame retardants (ADP particles) from the resin and weaken destructive effect during the processing. The SiR elastic shell layer also enabled a certain toughening effect on the ABS matrix, which can resist impact damage through the elastic deformation of silicone rubber shell structure. Specifically, the impact strength of 20ADP@SiR/ABS was 433% higher compared with 20ADP/ABS. On the other hand, 20 wt.% ADP@SiR achieved a LOI values to over 33% and UL 94 V-0 rating in ABS and decreased the heat release rate and total smoke yield by 61.4% and 28.8% compared to ABS, contributing by the gas and condensed phase synergistic effects of ADP@SiR. In the gas phase, ADP released phosphorus containing free radicals to quench combustion reaction. Meanwhile, SiR further facilitated the decomposition of ADP to exert quick flame retardant effect. In the condensed phase, SiR in ADP@SiR also promoted the formation of phosphorus containing fragments, which was able to interact with silicon fragments to exert P/Si synergy. Moreover, ADP@SiR significantly inhibited the smoke release of composites compared to ADP/ABS. Therefore, this study is meaningful practical exploration for developing the halogen-free flame retardant ABS composites with excellent toughness and flame retardancy.