We investigate the mechanical behavior of polypropylene/silica composites under mode I and II loading by using molecular dynamics simulations, focusing on the effects of two typical surface coupling agents of HMDZ and APTES on the interface deformation and failure. It is found that under mode I loading, the silica surface functionalized with APTES can enhance the tensile strength of polypropylene/silica composites effectively. In contrast, the silica surface functionalized with HMDZ has little effect on the tensile strength. The simulation results are supported by experiments. Under mode II loading, it is found that both HMDZ and APTES can enhance the shear strength of polypropylene/silica composites with APTES being more effective. The underlying mechanisms for the enhancement of interface strength are analyzed. Our work provides a deep understanding of the interface structure, deformation and failure and will be useful for selecting suitable surface coupling agents in enhancing the interface strength of polymer composites.

通过分子动力学模拟，我们研究了聚丙烯/二氧化硅复合材料在I和II模式下的力学行为，重点研究了HMDZ和APTES两种典型的表面偶联剂对界面变形和破坏的影响。发现在模式I加载下，用APTES表面官能化的二氧化硅可以有效地提高聚丙烯/二氧化硅复合材料的拉伸强度。相反，用HMDZ功能化的二氧化硅表面对拉伸强度的影响很小。仿真结果得到了实验的支持。在模式II加载下，发现HMDZ和APTES均可提高聚丙烯/二氧化硅复合材料的剪切强度，而APTES更有效。分析了增强界面强度的潜在机制。