Easier Ejection Through Use of Mold Release Coatings
Mold coatings with a permanent release action facilitate ejection of parts from the mold. This makes it possible to eliminate the need for large amounts of traditional mold release agents that are sprayed onto a mold’s surface in the form of solutions or dispersions – for instance, when processing PU.
Coating the mold by means of a low-pressure plasma technique is a successful approach that has already been used in the automotive industry to manufacture PU spray skins. For the purpose of coating, the mold is placed in a reactor where hexamethylide siloxane is broken down into reactive fragments in a plasma and then deposited onto the mold’s surface as a thin coating. The contours of the mold are replicated exactly, making the process ideal for textured surfaces, for instance.
During a recently concluded research project, it was possible to further improve the characteristics of the release coating. Faster and more uniform deposition of the coating yielded better results at corners and undercuts in the molds. It was also possible to increase the thickness of the coating by 100 %, while at the same time the amount of time needed to deposit the coating was shortened from four hours to one hour. As a consequence of the thicker coating, the abrasion resistance was also increased. Furthermore, use of release agent was reduced by an additional 10% compared to that with standard release coatings.
The researchers see future fields of application for molds with release coatings, for example, in production of rigid PU foam parts, injection molding of PU and TPE, rotational molding of PE and in the production of parts from carbon fiber-reinforced plastics.