Synthesis and thermal behavior of silica-graft-polypropylene nanocomposites studied by step-scan DSC and TGA

摘要

Silica graft poly(propylene) (silica-g-PP) nanocomposites were successfully prepared by radical grafting copolymerization and ring-opening reaction. Their thermal properties were studied by step-scan differential scanning calorimetry (SDSC) and thermogravimetric analysis (TGA). The exothermic peaks in the IsoK baseline (C-p,C-IsoK, nonreversing signal) of SDSC reveal that PP and silica-g-PP nanocomposites undergo melting-recrystallization-remelting during heating. The peak temperatures of recrystallization and remelting shift upward with the existence of nanoparticles in the PP matrix. The thermal degradation kinetics of silica-g-PP nanocomposites were investigated using nonisothermal TGA and the Flynn-Wall-Ozawa method. The results indicate that the thermal stability was significantly improved with increasing silica content, mainly because of the physical-chemical adsorption of the volatile degradation products on the nanoparticles that delays their volatilization during decomposition, and the covalent interaction between nanoparticles and PP chains, which will also reduce the breakage of PP backbone chains.