Phosphorus/Nitrogen Grafted Lignin as a Biobased Flame Retardant for Unsaturated Polyester Resin

摘要

Nowadays, polymers are widely used for various applications but have some disadvantages such as poor fire retardancy and thermal stability. However, some types of flame retardants for polymer have negative impacts on health and environment. Lignin, the second most highly abundant material from biomass, is one of the potential flame retardant for polymer. In this study, biobased flame retardant for unsaturated polyester (UP) was successfully fabricated from lignin using safer material. Lignin was functionalized using polyethylene imine and diphosphorous pentoxide to improve its fire retardancy and thermal stability. The chemical structure of functionalized lignin was characterized using FTIR and the results show that phosphate and nitrogen groups were successfully grafted on lignin. Based on UL 94 test results, we concluded that functionalized lignin using polyethylene imine and diphosphorous pentoxide can reduce burning rate of UP by 31.98% while the neat one reduced only as high as 22.87%. The TGA results also show that the functionalized lignin increases thermal stability of UP higher than the unfunctionalized one.