Abstract

In this study, we observed the effect of thermal degradation on the low-temperature sealing capability. A large-sized CR O-ring of 90.0 mm inner diameter and 7.0 mm cross-sectional diameter was used. In FT-IR spectroscopy, the aged CR O-ring, CR-10, showed a carboxyl group upon oxidation. Through oxidation, the sealing force of the aged CR O-rings decreased with an increase in the degree of degradation. As the degree of degradation increased, the 10% compressive modulus had higher values at each relative position. Oxidation was caused by oxygen diffusion to the CR interface. As the degree of degradation increased, glass transition temperature (Tg) was increased, and tanδ was decreased. CR-10 showed -44.0°C of Tg and 0.89 of tan δ. With an increase in the degree of degradation, the mobility of the CR decreased and showed a slow recovery rate at low temperatures. All specimens showed lower temperature retraction 10 (TR10) than Tg with 2.0-2.5°C difference. The gas leakage temperature increased with the degree of degradation. This coincided with Tg and TR10 tendency. Under Tg and TR10, CR could still exhibit viscoelastic properties and could be used as a seal. At the gas leakage temperature, the CR changed to a glassy state, and leakage occurred.

Keywords: CR O-ring;Low temperature sealing capability;Temperature retraction (TR);Glass transition temperature (Tg);Modulus profiles