Mechanism of bio-based halogen-free microcrystalline cellulose flame retardants

As a bio-based environmentally friendly material, microcrystalline cellulose (MCC) can be applied to automotive trims instead of traditional plastics; However, its flammable properties limit the application scope. In this paper, a multi-component environmentally friendly and efficient halogen-free flame retardant (APMMCC) was prepared by amino silicone oil (ASO)/phosphoric acid (H 3 PO 4 )/melamine (MEL) co-modification. The synergistic modification not only made the surface morphology of microcrystalline cellulose smoother, but also introduced ASO molecules, phosphoric acid and melamine groups, which altered its chemical structure. Thermal degradation tests showed that the thermal stability and char-forming ability of APMMCC were greatly improved. Compared with MCC, APMMCC had stronger combustion-resistance under the flame and showed significant flame retardancy. When the addition content of MCC and MEL is 1:1, the heat release rate, total heat release rate, and smoke release rate of APMMCC were minimized in the current research range. Moreover, the residual char of APMMCC at different temperatures was analyzed by Fourier transform infrared, and a condensed phase and gas phase synergistic flame retardant mechanism was proposed. Graphical abstract