WMV


Non stick coatings for industrial application

Non stick effects are mainly governed by the surface energy, structure,
and chemical reactivity. Especially mold release is significantly
influenced by the surface micro structure. However, melt flow is less
dominated by the surface energy.



Non stick


Lunac 1 and to some extent Lunac 2+ belong to the most effective non stick coatings to minimize sticking/degradation/die lines or melt fracture problems when applied to polymer processing machines. One of the best ways to determine the tendency of an organic material (e.g. plastics or food) in its ability to detach from a solid substrate is to determine the surface energy of the substrate. Reduced surface energy will lead to a weaker bond between these two phases (the machine/tool surface and the product). This force can be determined by measuring the angle between the (organic) fluid and the solid surface (see first figure). A larger angle will be established on materials with less 'sticking tendency'. See the following independent reports we obtained from a laboratory and end user. More detailed information on die line problems can be found in this document: melt conveyance directions.pdf






Diagram 1: The surface energies of various materials. Measured by the
German university for product engineering in Duisburg. Picture right,
the WMV contact angle/surface energy tester in use for
further product development.


























The non stick property of various materials and coatings have been assessed in a die
head test assembly of a plastic processing machine manufacturer. The applied plastic
was LDPE Lupolen 5021 at 18,33 Kg/h.







Melt flow is only partly controlled by the non stick effect


Generally the influence of low surface energy is over estimated in melt flow systems. Profound research at the university of product engineering in Duisburg revealed the more dominant influence of surface smoothness. Further melt flow improvement can be obtained by surface enhancement to very low roughness: e.g. Ra <0.005 µm / .0002mil. See diagram below. Still, pollution control and product release are still highly determined by the surface energy!


This diagram displays the amount of transparent HDPE needed to acquire the same
transparency before the pigmented HDPE was administered.







Orange skin effect




















SEM picture of RAD Lunac 1. Recently we discovered that Lunac 1 applied to a special sand blasted basic structure nucleates in just the right way to develop this ideal 'rounded off' micro structure. This structure can improve the non stick effect even further (especially in case of perpendicular product release). Sometimes (in case of rollers) the non stick effect can even be better than the non stick effect of a PTFE based system. The normal average roughness of this surface will be approximately 0.60 ┬Ám (0.024 mil) and consequently not applicable for highly polished molds or flow channels.













This extrusion die with an integrated filter disk has been coated with a non stick Lunac 1 coating. Second After teflon coatings, Lunac 1 has been proved to be the best way to minimize melt conveying, edge buildup and melt fracture problems. In application the major practical difference with teflon is the hardness and the 100% bond to the substrate. In this case the use of very expensive nickel alloys was banned as well.