Preparation of microencapsulated aluminum hypophosphite and flame retardancy and mechanical properties of flame-retardant ABS composites

Microencapsulated aluminum hypophosphite (MFAHP) with a shell of melamine-formaldehyde resin (MF) was prepared via in situ condensation polymerization. The presence of MFAHP increased the water resistance of flame-retarded (FR) acrylonitrile-butadiene-styrene (ABS) composites after hot water treatment. The mechanical properties indicate that the tensile strength and flexural strength of the FR ABS/MFAHP composites is enhanced with the incorporation of MFAHP. Cone calorimeter test results demonstrated that the peak heat release rate, total heat release, and total smoke release values of the ABS/MFAHP composites were significantly decreased. Digital photos and scanning electron microscopy images of the residues of ABS/25 wt % MFAHP(2) composites exhibited compact char layer structures, with many cobweb-like nanoparticle arrangements formed on the surface by the burning process. The investigation of flame-retardant mechanisms of ABS/MFAHP composites using infrared spectroscopy and energy-dispersive X-ray spectroscopy indicated that both the formation of char residue in the condensed phase and the release of inert gases by the MF shell in the gas phase led to the formation of compact and stable char layers containing carbon/pyrophosphate and aluminum polyphosphate, consequently leading to the good flame-retardant performance of MFAHP. (C) 2017 Wiley Periodicals, Inc.