常州大学材料科学与工程学院,江苏 常州 213164
Lignin-based char-forming agent (MLig) containing silica elements and carbon-carbon double bonds were successfully synthesized in one step using alkali lignin as a template and γ-methacryloxypropyl trimethoxy silane as a modifier. The results of thermogravimetric analysis (TGA) showed that MLig has better thermal stability and charring ability, which is significantly better than the unmodified alkali lignin advantage. MLig was used as a car-forming agent for the preparation of intumescent flame retardant polypropylene composites (MLig/IFR/PP). The flame retardancy, thermal stability and mechanical properties of flame retardant polypropylene were investigated by the limiting oxygen index analyzer, the vertical burning analyzer, thermogravimetric analyzer and electronic universal analyzer, respectively. The results showed that when the total addition of flame retardant was 30 wt% and the mass ratio of MLig to pentaerythritol was 1:3, the limiting oxygen index (LOI) value of MLig/IFR/PP could reach 32% and vertical burning UL-94 over V-0 rating, which was significantly better than intumescent flame retardant polypropylene with unmodified lignin (Lig/IFR/PP). Meanwhile, the flame retardancy of MLig/IFR/PP was still better than Lig/IFR/PP with 30 wt% flame retardant when the total amount of flame retardant added was reduced to 25 wt%. In addition, the thermal stability and mechanical properties of MLig/IFR/PP were improved compared with Lig/IFR/PP, in which the impact strength was improved by more than 80%. It can be seen that lignin-based car-forming agent has good application prospects in the field of intumescent flame retardant polymers.