Effects of Ammonium Polyphosphate on the Flame Retarding, Tensile, Dynamic Mechanical, and Thermal Properties of Kenaf Fiber/Poly(lactic acid) Biocomposites Fabricated by Compression Molding

Chopped kenaf fibers, poly(lactic acid) (PLA), and ammonium polyphosphate (APP) were uniformly compounded by twin-screw extrusion process, and then kenaf/PLA biocomposites with various APP loadings were fabricated by compression molding. The effects of APP on the flame retardant, tensile, dynamic mechanical, and thermo-dimensional properties were investigated. The biocomposites exhibit highly increased flame resistance, showing the limiting oxygen index increased with increasing the APP loading and the UL-94 V-0 level with 20 wt.% and higher APP loadings. The thermal stability of the biocomposites was increased, whereas the thermal expansion behavior was decreased with increasing the APP loading. The incorporation of APP into the PLA matrix contributed to simultaneously enhancing not only the flame retardancy, thermal stability, and thermo-dimensional stability, but also to enhancing the tensile and storage moduli of kenaf fiber/PLA biocomposites.