The thermal property and flame retardancy of RPC with a polyelectrolyte complex of nanocrystalline cellulose and ammonium polyphosphate

Polyelectrolyte complexes (PECs) with nanocrystalline cellulose and ammonium polyphosphate (NCC/APP) were prepared by an accessibly oriented self-assembly method, and the morphology and ultrastructure were investigated with transmission electron micrographs, scanning electric microscopy, Fourier infrared, and X-ray diffraction. The prepared PECs were then used as a flame-retardant system in rice straw-HDPE composites (RPC), and the thermal degradation, flame retardancy, and mechanical properties were studied by thermogravimetry, cone calorimetry, limited oxygen index (LOI) and mechanical testing. The thermal stability and flame retardancy of RPC were significantly influenced with an incorporation of PECs. PECs can promote the thermal degradation of RPC that take place earlier and stabilize the char residues. PECs can significantly improve the LOI of RPC, and LOI increased to 24.8% and 25.0% in the presence of NCC1/APP and NCC5/APP. PECs had a slight effect on heat release rate. PECs can also improve the mechanical property of RPC, and the tensile and flexural strength were increased with the addition of PECs of NCC/APP.