Improvement of the Cell Structure of Water-Foamed Liquid Silicone Rubber

This article shows three different water-based physical blowing agents for liquid silicone rubber (LSR) in terms of physical, mechanical, and morphological properties depending on the manufacturing parameters and amounts of blowing agents. The compositions consist of common LSRs added with pure water, water–silicone oil emulsion, and aqueous silicone. The foaming process is initiated in an injection molding process. By subvolumetrically filling the mold, it is possible to foam the LSR during the injection molding process. This publication aims to compare different, water-based blowing agents for LSR in the injection molding process. The results show that for all foams porosities between 0.25 and 0.4 are possible. An analysis of the foam structure shows that the aqueous silicone produces a significantly more homogeneous structure than the other two blowing agents. In addition, the mechanical properties are analyzed. For this purpose, tensile tests are carried out and the Shore hardness is determined. The elasticity and mechanical properties decrease slightly. The specific tensile strength also shows a small decrease, although this may be due to either the gradient of the foam structure or chemical reactions between the blowing agents and the LSR.