Surface microencapsulation modification of aluminum hypophosphite and improved flame retardancy and mechanical properties of flame-retardant acrylonitrile–butadiene–styrene composites

Abstract

Surface microencapsulated aluminum hypophosphite (SiAHP) was successfully prepared via the condensation polymerization of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane. The notched impact strength of the ABS/SiAHP composites was significantly enhanced compared to the corresponding ABS/AHP composites because the microencapsulated SiAHP improved the compatibility of SiAHP and the ABS matrix, and the vertical burning rate of the ABS composite with only 22.0 wt% SiAHP achieved V-0. The cone calorimeter tests demonstrated that the peak heat release rate (PHRR) and peak smoke production rate (PSPR) values of the ABS/22 wt% SiAHP composite were decreased by 81.1% and 49.5%, respectively, compared to those of the ABS/22 wt% AHP composite. Moreover, the total heat release (THR) and the total smoke production (TSR) values of the ABS/SiAHP composites were all lower than those of the ABS/AHP composites. These results clearly indicated that the silicone microencapsulation modification of SiAHP not only enhanced the flame retardancy efficiency of the FR ABS/SiAHP composite but also effectively restrained the smoke production rate of the ABS. A comparison of digital photographs and SEM images of the residues of the ABS/AHP and ABS/SiAHP composites after the cone calorimeter tests revealed that the residue of the ABS/SiAHP composites exhibited a denser and more compact surface char layer structure than that of the ABS/AHP composite. Energy-dispersive X-ray spectroscopy (EDS) measurement indicated that SiAHP more effectively promoted the carbon formation in the FR ABS composite at the surface compared to AHP. The three-dimensional compact char layer network containing C and Si effectively improved the flame retardancy of the ABS/SiAHP composite. Therefore, the flame retardancy of the ABS/SiAHP composite was attributed more to condensed-phase mechanisms than the flame retardancy of the ABS/AHP composite.