Thermal and fire behavior of natural fibers/PBS biocomposites

This paper investigates and compares the thermal degradation and fire reaction of different natural fibers and their corresponding biocomposites. Polybutylene succinate (PBS) was used as polymer matrix. Cellulose, hemp, flax, sugar cane and bamboo were used as natural fibers and ammonium polyphosphate (APP) was used as fire retardant agent. The influence of fiber type, fiber content and the addition of APP were investigated using TGA, PCFC and cone calorimetry.The incorporation of fibers in PBS reduces the thermal stability, and the time to ignition (TTI) of biocomposites, but it increases the mass residue corresponding to the formation of a char barrier. These results are ascribed to the components of fibers, and the flammability of the gas released by the lignocellulosic fibers. The fiber content does not influence the TTI, but affects significantly the peak of heat released rate (pHRR). Thus, a minimum content of fibers is required to form a protective barrier during fire test. The addition of APP in the biocomposite leads to hot hydrolysis of PBS and phosphorylation of flax. Hence, the fire retarded biocomposite forms a barrier layer due to the charring of the matrix and the preservation of the fiber skeleton and therefore shows a significant decrease of the pHRR.