The reflectivity, wettability and scratch durability of microsurface features molded in the injection molding process using a dynamic tool tempering system

Abstract

In this paper the replication qualities of periodically and randomly arranged micro-features molded in the injection molding process and their effects on surface properties are studied. The features are molded in PC, PMMA and PP at different mold wall temperatures in order to point out the necessity and profitability of a variotherm mold wall temperature control system. A one-dimensional heat conduction model is proposed to predict the cycle times of the variotherm injection molding processes. With regard to these processes, the molding results are compared to the molded surface feature heights using an atomic force microscope. In addition, the effects of the molded surface features on macroscopic surfaces are characterized in terms of light reflection using a spectrometer and in terms of water wettability by measuring the static contact angle. Furthermore, due to the sensitivity of the surface features on the molded parts, their durability is compared in a scratch test with a diamond tip. This leads to successful implementation in applications in which the optical appearance, in terms of gloss and reflection, and the water repellence, in terms of drag flow and adhesion, are of importance.

Scratch tests on micro-structured polymer surfaces produced by injection molding and reaction processes

“…Both the heating and cooling units for a variothermal process control are placed behind the structured mold walls inside the cavities (see figure 3). For further details see Kuhn et al (2010Kuhn et al ( , 2011.…”

“…Surface structures can be applied in the form of specific functional structures, e.g. optical gratings, fluidic channels (see figure 1(a)) and more general surface structures (see figure 1(b)) are often used to modify surface properties such as light reflection, wettability of liquids, haptic feel, drag flow or frictional behavior (Kuhn et al 2011). Furthermore, topological and chemical modifications become important at micro-scale where the performance is mainly attributed to the surface properties (Singh et al 2006).…”