Controllable Synthesis of a Well-defined Polypropylene grafted Silica Nanoparticles and Its Effect on Crystallization Behavior of Polypropylene

Well-defined polypropylene grafted silica nanoparticles (PP-g-SiO2) were prepared through the reaction of maleic anhydride grafted polypropylene (PP-g-MAH) with amino-functionalized silica (SiO2-NH2) by the 'grafting-to' method. The grafting density of PP-g-SiO2 is found to be controlled by the concentration of silane coupling agent 3-[2-(2-aminoethylamino) ethyl amino] propyl trimethoxy silane (TAMS). The maximum grafting density of grafted PP-g-MAH chains with molecular weight of 9100 g/mol could reach 0.34 chains/nm(2), when the critical concentration of TAMS was 0.0194 mol/L. The critical concentration of TAMS can be explained by the maximum amounts of primary amino groups, which can totally react with PP-g-MAH on the surface of SiO2-NH2, when the silane monolayer is formed. The synthesized PP-g-SiO2 with different molecular weights was mixed with PP by solution mixing to form a series of nanocomposites. The crystallization temperature (T-c) of nanocomposites increased significantly with the particle loading. The PP-g-SiO2 with high molecular weight of grafted chains exhibits a high nucleation ability at 1 wt% nanoparticle loading in PP/PP-g-SiO2 nanocomposites. In summary, we provide an effective method to synthesize the well-defined PP-g-SiO2 with controlled grafting density, which shows excellent nucleation ability.