Flame retardancy mechanism of poly(butylene terephthalate)/aluminum diethylphosphinate composites with an epoxy-functional polysiloxane
The flame retardancy of poly(butylene terephthalate)/aluminum diethylphosphinate (PBT/AlPi) composites was greatly enhanced by the incorporation of an epoxy-functional polysiloxane (EPM). The limiting oxygen index (LOI), vertical burning (UL 94), and cone calorimeter test were performed to evaluate the flame-retarded effect. The PBT composite containing 11 wt% AlPi attained a V-0 rating of 37.1% in the UL 94 test with LOI and with the aid of 0.6 wt% EPM. The flame-retarded mechanism of the PBT/AlPi/EPM composite was also proposed from the results of the cone calorimeter test, TGA, TGA-FTIR, SEM micrographs, and SEM/EDX analysis of the residues. The introduction of small amounts of EPM greatly encouraged the formation of cross-linking char residue. The condensed-phase action was proposed to be the dominant flame-retardant role of the PBT/AlPi/EPM composite.