Absorption of Silicone Oil by a Dimethylsiloxane Elastomer

Abstract

Abstract Polydimethylsiloxane elastomer immersed in DC 200 silicone oil at temperatures of 180–200°C absorbs oil by two concurrent processes, a rapid and reversible diffusion process and a slower, irreversible process resulting from the chemical degradation of the sample. Absorption by diffusion reaches equilibrium in 200 h, and the absorption capacity depends on the amount of curing agent used in the preparation of the elastomer composite. The oil absorbed during this period can be removed by extraction. The absorption capacity is less for the elastomer composites containing silica and decreases linearly with the volume fraction of elastomer in the sample, indicating that only the elastomer absorbs oil. The rate of absorption depends on t1/2 and has a weak temperature dependence. The diffusion coefficients are in the range 10−12 m2/s, and do not seem to be affected by the presence of filler. While the diffusion of oil does not appear to produce chemical changes in the elastomer, the elastomer is gradually destroyed by the slower chemical process, which promotes the absorption of additional amounts of oil.