Plate impact experiments on the silicone elastomer DC745U cooled to -60°C

Using gas-gun-driven plate impact techniques, we have measured the Hugoniot of the filled silicone elastomer DC745U cooled to -60°C. DC745U consists of approximately 62 weight% poly-dimethyl-siloxane rubber and 38 wt% silicon dioxide filler. At ∼-50°C, the poly-dimethyl-siloxane rubber in DC745U crystallizes with ∼ 40% crystallinity. This is accompanied by a density change from 1.31 g/cm³ at 23°C to 1.45 g/cm³ at -60°C. Below the crystallization transition temperature, a measurable increase in the shock velocity was observed. This is coincident with a decrease in compressibility due to crystallization of the polydimethylsiloxane repeat units. The linear U_S - u_p Hugoniot also significantly changes from U_S=1.62+1.74u_p mm/µs at 23°C to U_S=2.00 ± 0.05+(2.06 ± 0.06)u_p mm/µs at -60°C. Cooling to -60°C and the associated crystalline phase transition therefore results in considerable stiffening. This is the first time, to our knowledge, that a polymer crystallization transition has been shown to affect shockwave properties in this way.