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Nano-injection molding technology is an important method for large-scale production of metal-polymer composites of various shapes. The mechanical properties of these materials are closely related to the interfacial process. In this work, polyphenylene sulfide (PPS) and copper (Cu) were selected as candidate polymer and metal materials, and constructed four different polydopamine (PDA) coatings, including monomer, dimer, linear tetramer, and cyclic tetramer, to modify metal surfaces. The molecular dynamics simulations were launched to investigate the interaction behavior of heterogeneous interfaces during nano-injection molding and the mechanism by which polydopamine affects the adhesion behavior at the copper-polyphenylene sulfide interface. Results showed that the addition of polydopamine caused the polymer chains to form many anchor points on the contact surface, which inhibited the wall-slip behavior of the polymer and led to a mushroom-like movement of the polymer on the wall surface. The interfacial energy, filling rate data revealed that polydopamine contributes to the enhancement of interfacial adhesion properties, and the polydopamine dimer structure is the most effective of the four configurations. The enhancement of interfacial adhesion mainly originates from the enhancement of non-bonding interactions and entanglement anchoring between PPS-PDA. Highlights * Polydopamine coating inhibits polymer slip behavior in nano-injection molding. * Polydopamine enhances bond strength of metal-polymer composites effectively. * Dopamine dimers have better adhesion properties than other structural dopamine. * Polydopamine coating alters the adhesion mechanism at heterogeneous interfaces. * The interface failure mode was closely related to the stress loading mode. KEYWORDS anchoring behaviors, Interface, molecular dynamics simulation, nano-injection molding, polydopamine, 1 | INTRODUCTION With the rapid advancements in micro and nanotechnology, there has been a increasing demand for the production of miniaturized and precisely engineered products. The concept of 'micro' [...]

Abstract This work focuses on the development of a novel thermo-responsive shape memory polymer (SMP) for 4D printing by blending polycaprolactone (PCL) and poly(ethylene-co-octene) (POE) in various proportions. The SEM [...]

Polyphenylene sulfide (PPS) and copper (Cu) were used as the polymer and substrate material to simulate the nano-injection molding process by molecular dynamics method. The results show that the PPS chain obeys Einstein’s diffusion law in the early stage of injection molding then deviates from it in the late stage due to the entanglement and limitation of surrounding nanoparticles. In addition, the process of conformational isomerization of polymer chains is accompanied by the twisting and stretching of fixed chains. There are two kinds of adhesion phenomena, one is the macromolecular slides violently in small areas of some sure nanoscale groove to form multiple anchor points. The other case involves multiple nano-grooves along the metal interface, the polymer chain slides and is bolted as multiple anchors in different grooves due to the exerted wall-drag effect on the neighboring chains. These two slipping and anchoring mechanisms are consistent with de Gennes’ slipping theory. Through the quantitative analysis of the influence of pressure on injection filling, it is found that injection pressure should be kept within a certain range to achieve the positive effect of molding.

This study focuses on investigating interfacial interactions and the adhesion mechanism of polymer-metal interfaces in nano-molding. Polyphenylene sulfide (PPS), polyamide 6 (PA6), and isotactic polypropylene (iPP) were chosen as candidate polymers, and aluminum (Al), and copper (Cu) were used as metal substrates. By establishing the metal matrix composed of a rectangular pit with length, width, and depth of 4.5, 4.5, and 2.0 nm, respectively, six paired polymer-metal interfacial systems in a cuboid of 7.5 * 7.5 * 11.5 nm, consisting of metal, polymer, and vacuum layer (from bottom to top) were constructed. Molecular dynamics simulations were performed to calculate interfacial interactions and bonding processes. Results showed that wall-slip behavior was pronounced in nano-molding. Viscoelasticity and polarity of the polymers played a crucial role in interfacial interactions, which guided the wall-slip behavior and greatly affected the bolt performance. PA6 and PPS were more suitable for molding than iPP on both Al and Cu substrates. PA6 showed the best filling and bonding performances, followed by PPS, while iPP revealed the poorest performances. The Cu substrate exhibited better anchor strength and filling rate than Al substrates with the same polymer. KEYWORDS adhesion, injection molding, interactions, molecular dynamics, 1 | INTRODUCTION The interest in manufacturing polymer-metal integration products by means of injection molding is increasing due to the advantages in productivity and cost effectiveness. [1-3] By combining metals [...]