Processing of liquid silicone rubber (LSR) in the injection molding process has a high economic potential. Since there are some fundamental differences compared to classical thermoplastic injection molding, up to now there is a lack of well-founded knowledge of the process which allows an

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The use of cross-linking polymers such as liquid silicone rubber (LSR) can replicate serviceable surfaces with nano- and microstructures via the injection molding process. Laser ablation can be used to introduce microstructures into molding tools, while nanostructures are generated via PVD coating processes on the tools. This is why nanostructures are built using self-organized layer growth. The aim of this study was to generate evidence of direction-dependent coefficients of friction of elastomeric surfaces in dry or lubricated contact in boundary friction. Models of the dry friction of elastomeric surfaces, such as Schallamach waves or stick-slip cycles, were used to describe the friction modulation of such surfaces. Assumptions for model contacts against smooth partners, both dry and with lubrication, as well as assumptions for the interaction of structures with smooth surfaces, were investigated. It was found that for elastomer surfaces with Shore hardness 50, nanostructures are suitable for creating a direction-dependent friction increase in static and sliding friction. Friction reductions with defined microstructures are possible if their periodicity seems to interact with the wavelength of possible Schallamach waves. The choice of lubrication determines the forced wetting of the contact, but due to the structuring, there is a continuous transition to mixed friction.

The processing of liquid silicone rubber (LSR) in the injection molding process to molded parts offers high economic potential due to its great scalability.Unlike the well-researched and understood injection molding process of thermoplastics, LSR still lacks basic process knowledge. The cavity pressure curve shows a completely different pattern, as the cold LSR expands strongly once placed in the hot mold due to volume dilation. During processing of LSR exothermic and irreversible cross-linking, occurs. In this work, a method is introduced to display the cross-linking reaction in the cavity pressure curve. Using a self-developed testing device and conventional differential scanning calorimetry measurements, a correlation between cross-linking and the pressure signal can be demonstrated. A typical deflection is evaluated in the pressure curve by differentiating, which is attributed to the cross-linking. The relationships established are confirmed by pressure measurements in the mold during the processing of LSR in the injection molding process. The knowledge gained contributes to a better understanding of the process, helps to optimize existing processes and save resources. Existing cavity-pressure-measuring-systems are to be supplemented by an evaluation logic and thus, in addition to cycle time optimization, process variations are to be detected, energy consumption optimized and quality ensured and verified.

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