MD simulation analysis of the anchoring behavior of injection-molded nanopits on polyphenylene sulfide/Cu interface

Polyphenylene sulfide (PPS) and copper (Cu) were selected as candidate materials for modeling a nano-injection molding process. Four nanopit shapes (rectangular, cylindrical, pyramidal and conical) were modeled to investigate the PPS/Cu heterogeneous interface. By using molecular dynamics simulations, the influence of the nanopit structure on the interactive behavior and bonding performance of the polymer/metal interface in injection molding was determined. Results show that polymers were more easily injected into nanopits with slope or rounded boundaries, such as the cylindrical and conical interfaces. In the early stages of molding, the PPS chains followed the Einstein diffusion law, while in the later stages, PPS chain behavior deviated from the law due to entanglement and limitations of the nanopits. Compared with pyramidal and conical nanopits, the rectangular and cylindrical nanopits were not well-filled in their middle and lower layers. The filling rate of the bottom-most layer was better than that of the incompletely filled layers because of polar adsorption and wall-slip phenomena. Compared with other interfaces, the conical nanopits had relatively irregular lattice arrangements and a higher level of lattice defects. This led to an increase in the interfacial energy and wettability, which was beneficial to the adhesion performance of the PPS/Cu interface.