Creep Mechanical Performance of Cryogenically Aged PTFE at Room Temperature

Due to excellent performance, polytetrafluoroethylene (PTFE), being sealing material, is widely used in chemical engineering, aerospace engineering, mechanical engineering, civil engineering, energy engineering and other sectors. However, due to obvious temperature drops in supplying or storing fluids, the mechanical behavior of PTFE under cryogenic conditions is still unclear. In this study, the creep mechanical performance of PTFE gaskets after cryogenic aging in liquid oxygen is experimentally investigated. The circular PTFE gasket samples are immersed into liquid oxygen for cryogenic aging treatment. The universal testing machine is utilized for material mechanic tests. Three different load levels, including 10 MPa, 15 MPa and 20 MPa, are designed and accounted for. It is found that the creep strain of PTFE exhibits three typical stages, namely the initial rapid increase phase, transition phase with a reducing growth rate, and stable linear growth phase. Moderate cryogenic immersion aging can effectively improve the creep resistance of PTFE, but excessive aging treatments will lead to mechanical property degradation of PTFE. The Burgers life prediction model is improved by introducing a nonlinear correction term, which can accurately predict the creep behavior of PTFE under different aging states. The present study can provide experimental evidence and a theoretical basis for a deep understanding of the mechanical response of PTFE materials under extreme cryogenic intermittent service conditions.