Abstract Low-friction mold surface coatings can be used to promote filling of thin-wall parts through reduction of the melt flow resistance by causing wall slip at the polymer-mold interface. This work investigates the effects of different mold coatings (DLC, CrN and CrTiNbN) on the flow resistance of molten polystyrene in thin-wall injection molding. The design of the mold allowed high-speed visualization of the molten polymer flow during the filling phase and measurement of the velocity profile across the cavity thickness. The evaluation of the speed profiles allowed the characterization of the wall-slip phenomenon, indicating the absence of conventional ‘fountain-flow’ filling mechanism. The results indicate that a DLC deposited on a chrome substrate can significantly reduce the flow resistance of polystyrene, by increasing the slip velocity of polymer melt in contact with the mold surface. Moreover, the contact angle of molten polystyrene over the considered coatings was found to be inversely proportional to the melt flow resistance, indicating the importance of the adhesion at the polymer-mold interface.

中文翻译：

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带有涂层和未涂层​​腔体的聚苯乙烯部件的薄壁注塑成型

摘要 低摩擦模具表面涂层可通过在聚合物-模具界面处引起壁面滑动来降低熔体流动阻力，从而促进薄壁零件的填充。这项工作研究了不同模具涂层（DLC、CrN 和 CrTiNbN）对薄壁注塑成型中熔融聚苯乙烯的流动阻力的影响。模具的设计允许在填充阶段高速可视化熔融聚合物的流动，并测量整个型腔厚度的速度分布。对速度曲线的评估可以表征壁滑现象，表明没有传统的“喷泉流”填充机制。结果表明，沉积在铬基材上的 DLC 可以显着降低聚苯乙烯的流动阻力，通过增加与模具表面接触的聚合物熔体的滑移速度。此外，发现熔融聚苯乙烯在所考虑涂层上的接触角与熔体流动阻力成反比，表明聚合物-模具界面处的粘附性的重要性。