Molecular Dynamics Investigation of the Shearing Behavior of Short-Chain Additives at Nanoscale Rough Ceramic/Polymer Interfaces: Implications for Biomedical Applications

The shearing behavior between ceramics and polymers is crucial for the performance of composite materials, especially in applications like total knee replacement, where it significantly impacts the wear and durability of artificial joints. However, the atomic evolution mechanism at the interface during shear and the key influencing factors at the nanoscale are not fully understood. To address this, we use a molecular dynamics approach to model the shearing behavior of short PP chain additives at the SiO₂/PP interface, focusing on the underlying mechanisms and key factors under both smooth and rough nanoscale interface conditions. The results show that the rough interface, with its nanoscale roughness, induces significant shearing deformation in the PP chain additives due to the hindering effect of SiO₂, whereas the smooth interface exhibits minimal deformation. As a result, the rough interface exhibits higher interfacial shearing stress. The study further examines the impact of nanoscale interface roughness, finding that increased roughness (larger amplitude or smaller wavelength) intensifies the obstructive effect on the PP chain, leading to larger shear deformation and higher shear stress. Additionally, the effect of loading velocity is considered. Within typical loading velocity, the impact on shear behavior is negligible, with significant effects only occurring when the velocity exceeds several hundred meters per second. Finally, we propose that forming a cross-linked network from short-chain PP can serve as an approximation for long-chain PP materials, and we discuss the effects of cross-linking. The findings provide valuable insights into the behavior of short-chain additives at nanoscale rough interfaces and contribute to the understanding of interfacial friction and wear, particularly in applications such as total knee replacement in the field of biomedical applications.