LSR foams made with water as blowing agentThursday (08.10.2020) 16:50 - 17:10
Liquid silicone rubber (LSR) has good chemical and physical properties, in particular, it is biocompatible and weather-proof and it can be used between -50°C and 200°C. It is used in the automotive sector, for household, babycare and in medical devices. However, it is more expensive than other elastomers. For this reason, the density should be reduced to get lower the price for parts. By producing LSR foams, the density can be reduced to below 1 g/cm³. Besides, the haptics of the components and the thermal insulation properties are improved.
LSR is processed by liquid injection molding (LIM). Due to this processing method, the blowing agent has to expand inside the hot mold (150°C up to 200°C) to create the foam structure. Possible blowing agents are physical blowing agents such as water or watery pyrogenic silica. The foam structure depends on the different blowing agents and their amount as well as on the processing parameters. This structure influence the mechanical properties like the shore hardness and the tensile strength. In comparison to the full LSR-material, the foam has a reduced effective cross-section. This leads to a decreasing in the tensile strength. The shore hardness decrease, too. The air inside the pore structure can be compressed easier than the matrix material and this leads in the lower hardness. The important value is the weight, which can be reduced up to 35%.