Preparation of High Loading Magnesium Hydroxide Flame Retardant Polypropylene by Solid State Shear Milling

Due to high loading level and poor compatibility, magnesium hydroxide (MH) flame retardant polypropylene (PP) has poor processability and seriously deteriorated material performance. We adopted a novel processing technology, solid state shear milling (S3M) by using our self-designed pan-mill equipment, to prepare even MH/PP composite powder, as the flame retardant master batch to be added to the virgin PP. This original method can achieve efficient pulverization of PP, a high degree of blending, and even dispersion of MH in the resin, thus effectively controlling the dispersion phase in solid state. Simultaneously, mechanochemical effects of S3M can induce chemical interaction between PP and MH, and improve their compatibility. Compared with conventional melt processing, S3M can greatly enhance the melt flowability, and greatly modify the melt processability of the composite materials. Also, pre-compounded through S3M, MH flame retardant PP shows remarkably enhanced flame retardancy and mechanical performance, therefore showing promise to prepare high performance composite materials with high loading level for commercial applications.