Interactive effect of ammonium polyphosphate and montmorillonite on enhancing flame retardancy of polycarbonate/acrylonitrile butadiene styrene composites

Abstract

The effect of two flame retardants [ammonium polyphosphate (APP) and montmorillonite (MMT)] was studied in relation to flame retardancy, mechanical properties and physical characteristics of polycarbonate (PC)/acrylonitrile butadiene styrene (ABS) blends. Moreover, the possible synergistic effect of these two flame retardant additives on the macromolecular blends was studied as well. Based on this research, it was revealed that APP- and MMT-raised loading has significantly increased the limiting oxygen index (LOI) of the resulting PC/ABS blends, which is due to the intumescence effect provoked by the incorporation of these flame retardant fillers. Incorporation of APP improved the LOI through intumescence effect while the addition of MMT led to intercalation of PC/ABS polymer matrix into the interlayer galleries of MMT particles. Besides, higher APP loading in PC/ABS blends has significantly promoted the formation of carbonaceous char residues as evidenced in TGA analysis, which indicates that addition of higher APP could improve thermal stability of PC/ABS blends. To improve the tensile strength and elongation-at-break, APP loading of 25 phr in PC/ABS blends together with various MMT loading would be suitable to ensure good dispersion and interfacial adhesion between the polymer chains and the additives. However, it is important to control the loading level of MMT as its excessive incorporation could result in flame-retarded PC/ABS blends with brittle behavior, showing weaker mechanical properties.