Flame retardancy and synergistic flame retardant mechanisms of acrylonitrile-butadiene-styrene composites based on aluminum hypophosphite

A series of flame retardant acrylonitrile-butadiene-styrene copolymer (FR ABS) composites were prepared by melt blending using aluminum hypophosphite (AHP) and melamine cyanurate (MCA) or silicone flame retardant (SiFR) as synergistic flame retardant. The thermal behavior, flame retardancy of FR ABS composites were investigated by thermogravimetric (TGA), the UL-94 vertical burning test, limiting oxygen index (LOI) and cone calorimeter test. The FR ABS composite showed good flame retardancy, from no vertical rating of ABS to V-0 rating of FR ABS containing 25 wt% AHP in the UL-94 test. The results showed that ABS/22wt%AHP composites presented lower peak heat release rate (PHRR), lower total heat release (THR) and higher char residue (CR) than those for ABS. Adding small amount of MCA or SiFR, PHRR and THR values for ABS/20wt%AHP/2wt%MCA and ABS/20w%AHP/2wt% SiFR composites decreased compared with ABS/22wt%AHP composite, which indicated that the incorporation of MCA or SiFR led to a synergistic effect on the ABS/AHP flame retardant composites. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) measurement results showed that the residual structure for ABS/20wt%AHP/2wt%MCA and ABS/20wt%AHP/2wt%SiFR composites presented very different surface morphology and surface element composition, which were attributed to different synergistic flame retardant mechanisms. (C) 2014 Elsevier Ltd. All rights reserved.