Macro-Microscopic Characterization and Long-Term Performance Prediction of Polyvinyl Chloride Under Hydrothermal...

The creep behavior of rigid polyvinyl chloride (PVC) in hydrothermal environments can compromise its long-term stability and load-bearing capacity, potentially leading to deformation or structural failure. Understanding this degradation is critical for ensuring the durability and safety of PVC in engineering applications such as pipelines and building materials. In this study, accelerated hydrothermal aging tests were carried out on PVC under controlled conditions of 60 °C and 90% relative humidity (RH). Short-term tensile creep tests at four different stress levels were conducted both before and after aging. Microstructural changes associated with the PVC's creep behavior were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and other microscopic characterization techniques. These analyses provided a detailed microscopic interpretation of how hydrothermal exposure and applied loads influenced the macroscopic creep performance of the PVC, thereby elucidating the correlation between its macroscopic mechanical behavior and microstructural evolution. By applying the time-stress equivalence principle and the time-aging equivalence principle, the short-term creep behavior was characterized to predict long-term performance. The accelerated characterization curve can effectively predict the creep behavior of PVC under a stress level of 16 MPa over approximately 6.5 years in an environment of 60 °C and 90% RH. At the same time, the master creep modulus curve of PVC under any aging duration and stress level can be established under the specified environmental conditions of 60 °C and 90% RH. Long-term creep curves were fitted using a locally structured derivative Kelvin model, demonstrating that this model can effectively simulate the long-term creep behavior of PVC under hydrothermal conditions. The results indicate that at a stress level of 16 MPa, PVC is expected to undergo creep damage and failure after approximately 15 years in such an environment. These findings provide a critical reference for assessing the long-term performance of PVC in hydrothermal environments.