Measurement of the viscosity of irradiated silicone using a differential viscometer

High-energy electron (2.0 MV) and gamma irradiation (Co-60) has been used t o modify polymeric silicone fluids of initial viscosities in the range, 90- 700 cSt. Doses of electron and gamma radiation were delivered at rates of 0 .246 kGy s(-1) and 15 kGy h(-1), respectively, exposure times being adjuste d to ensure energy deposition in the range 30-360 kGy. Measurements were ma de using a differential viscometer based on a Bose Institute design. In lin e with expectation, samples of greater initial molecular weight land hence greater viscosity), were observed to be more susceptible to radiation induc ed cross-linking than those of lower molecular weight, The role of dose rat e and oxygen diffusion in determining the extent of change is discussed. (C ) 2000 Published by Elsevier Science Ltd.