Combustion properties and transference behavior of ultrafine microencapsulated ammonium polyphosphate in ramie fabric-reinforced poly(L-lactic acid) biocomposites

Flame-retardant biocomposites have attracted much attention in past decades. They can provide many advantages, such as total biodegradability and their abundant renewable sources. In the work reported, biocomposites based on poly(L-lactic acid) (PLLA), ramie fabric (FAB) and microencapsulated ammonium polyphosphate (MCAPP) were synthesized via hot press molding using the powder-stacking procedure. The effects of transference behavior of the flame retardant on sustaining flame retardancy of the biocomposites were investigated. Thermogravimetric analysis shows that the improved flame retardancy is due to an increased char residue at high temperature. Field emission scanning electron microscopy images and wide-angle X-ray diffraction data were used to investigate the hydrolysis reaction and transference behavior of ammonium polyphosphate in the biocomposites. UL-94 testing and limiting oxygen index measurements show that the PLLA/FAB/MCAPP biocomposites retain their flame retardancy even after 21 days in UV-irradiation hydrothermal aging tests. The good sustained flame retardancy of the PLLA/FAB/MCAPP biocomposites is attributed to the docking interactions and good distribution of MCAPP in the biocomposites. (C) 2010 Society of Chemical Industry