Evaluation of the Compatibility and Physical Properties of Silicone Elastomer Containing Hydrophilic and/or Hydrophobic Additives

Abstract

Hydrophilic additives viz water, PEG 200, 400 and 600 have been successfully incorporated into medical grade silicone elastomer via the pre-formation of a water-in-oil emulsion. The formulation, including an emulsifier, has been optimised and hydrophilic particles of low, narrow size distribution incorporated into the silicone matrix. These additions were shown to have insignificant effect on the curing characteristics of the polymer. Various amounts of PEG were loaded into the elastomer and physical properties measured. There was no significant variation in these properties for the PEG MWt range chosen. However, at high loadings (greater than 20 wt %) these properties are significantly reduced. The use of such a system for incorporating, and subsequently controllably releasing hydrophilic drugs, is discussed.