Figure 1. Morphology of various polydimethylsiloxanes

One of the newest and most rapidly growing classes of silicones used in skin care applications is silicone elastomers, which are made by cross-linking dimethicone polymers to produce elastomeric solids that have properties quite different from dimethicone fluids. As the degree of cross-linking increases, the silicone network becomes more rigid. Although they are produced by a different process, silicone resins can be thought of as representing the most extreme examples of cross-linked silicone polymers. Silicone resins have a tight, three-dimensional structure that results in rigid materials that can form hard, durable films. Figure 1 illustrates variations in polydimethylsiloxane morphology based on increasing molecular weight and cross-linking.