An eco-friendly and effective approach based on bio-based substances and halloysite nanotubes for fire protection of bamboo fiber/polypropylene composites

Bamboo fibers (BF) have great potential as reinforcement for polypropylene (PP)-based composites and are a renewable and sustainable alternative to synthetic fibers. However, the high flammability greatly limits their industrial applications. Here, a feasible and environmentally benign strategy for fabricating fire-safe BF/PP composites was developed by decorating BF/PP non-woven mats with a halloysite nanotubes (HNT) layered structure enabled by layer-by-layer (LbL) assembly of biobased chitosan (CS) and phytic acid (PA), followed by hot-pressing. The resulting BF/PP composites (BPC-6BL) exhibited excellent flame resistance with a significant reduction in the peak heat release rate (45.3%) and total smoke production (58.8%) than the control, as well as enhanced thermal stability with a higher char yield (17.8%). The analysis of volatile gases and char residues suggested that the enhanced flame retardancy was due to the condensed-phase and gaseous-phase mechanisms caused by CS/PA and HNT synergistically. In addition, the mechanical and water resistance properties of the BF/PP composites (BPC-3BL) were improved substantially compared to the control. Taking advantage of these features, this flame retardant approach based on natural mineral and bio-based resources would improve the potential applications of BF/PP composites to automotive interiors and construction industries.