Study on microscopic mechanism of nano-silicon dioxide for improving mechanical properties of polypropylene

Abstract

ABSTRACTAn unmodified polypropylene (PP) model and a modified model with 2% nano-silicon dioxide content were built initially, and then the mechanical parameters of the two models were compared by molecular dynamics simulation. The results show that the modulus of the modified model are larger than those of the unmodified model, and the ductility of both models is stable. The yield point of the modified model was increased by 8.5% at 25°C and 14.2% at 100°C compared with that of the unmodified model, respectively. Its Young's modulus is also increased. The main mechanism is that the addition of nanoparticles results in the decrease in the free volume of PP molecules, and the interaction between the strong polar –OH groups and the H atoms in a large number of –CH3 groups in PP molecules increases the intermolecular force in the whole model, which leads to the improvement of mechanical properties. Higher temperature leads to the intensification of molecular motion, which increases the distance between molecules, decreases the cohesive energy and reduces the mechanical properties of the model. The results of this paper can provide some reference for further research on the improvement of mechanical properties of nano-doped modified materials.