Changes in silicone polymeric fluids due to high-energy radiation

Abstract
When subjected to high-energy radiation, polydimethyl siloxanes can be cross-linked to form insoluble amorphous structures which are transparent and have marked rubber-like properties. Data are given on the relation between molecular weight and bulk viscosity, which is often used to characterize these polymers. The relationship between cross-linking density and radiation dose is deduced from the changes in both solubility and fusibility, and is confirmed by elastic measurements. Unit pile radiation is found to produce cross-linking in about 2$\cdot $2% of the monomer units. Details are given of the change in solubility and swelling with radiation dose and of the mechanism of cross-linking. The energy per cross-link is about 32 eV, and is independent of molecular weight. A brief comparison is made with cross-linking in hydrocarbon polymers.