SMTA International Conference Proceedings

Silicone Pressure Testing: Thermal Expansion and Solvent Swelling

Author: Kent Larson
Company: Dow Chemical Company
Date Published: 9/17/2017   Conference: SMTA International

Abstract: Silicones are well known for having a large expansion when they are heated and contraction when cooled based on their relatively high Coefficient of Thermal Expansion (CTE). They are also known for their chemical stability, though they do have a tendency to swell when exposed to soluble (fairly non-polar) liquids. Both volumetric expansions create pressure when the silicone material is in a confined space.

Measurements show that when confined samples of silicone gels and soft elastomers (low to mid-00 scale hardness) are heated, they create pressures that track closely with what would be expected from liquids, while A scale hardness silicones create pressures that more closely follow elastomer predictions. Solvent swelling in confined samples produced very similar results, though the measured data for the harder elastomers fell between the liquid and elastomer predictions. Within the limited data, it appears that the crossover between liquid and elastomer pressure generation behavior lies somewhere in the upper 00 / 1-10A hardness scales, or in the 0.2 – 0.5 MPa Young’s modulus range. Details are provided to allow for pressure generation estimates for both thermal expansion and liquid swell.

Key Words: 

CTE, expansion, pressure, swelling

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