Nanostructured Coatings in Micromoulding Injection – A Case Study☆

Microinjection moulding has been in continuous growth due to its ability to quickly and inexpensively produce large amounts of microparts. Nevertheless, downscaling the macro-injection process requires a thoughtful comprehension of the physics underlying microinjection moulding. High surface-to-volume ratios in microparts require higher injection pressure and injection speed to prevent premature solidification. In these conditions, the interaction between the melt and mould channels are critical, due to the increase of friction, wear, or even adhesion, leading to a deterioration of the quality of the micromouldings. Proper coatings, with high wear resistance and heat transfer capacity and low friction coefficient at injection molding temperatures, may assist microinjection moulding. In this work, the behavior of polymeric flow in microcavities coated with nanocrystalline diamond is investigated. It is showed that the front flow benefits from the coating. Additionally, it is suggested that the diamond coating can act as a heat buffer, assisting the heat transfer mechanism in the polymer/mould interface at the flow stage.