The deformation mechanism and phase transition behavior of polytetrafluoroethylene (PTFE) under stretching conditions (25, 50, 100 °C) were investigated by using differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and X-ray diffraction (XRD).

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Fluoroelastomer (FKM) has been widely used in aerospace and some particular fields, whose aging is a key problem to influence the service life of the systems. The aging behaviors of FKM in the lubricating oil have been investigated in our previous study. In this work, the influence of intentionally aged or oxidized lubricating oil (A‐O) on the aging process of FKM is reported for the first time comparing with the situation in the fresh oil (F‐O). As the oil medium aged at 200°C for different time, its color, acid number and contact angle with FKM change evidently indicating possible oxidation might occur although the Fourier transform infrared spectrometer (FTIR) has little change. Then, the influence of aged oil medium on the aging behaviors of FKM was further examined. Compared with F‐O, the aging process of FKM in A‐O was significantly accelerated as evidenced by FTIR, tensile strength, mass change, DMA, and macroscopic observation. With the increase of aging temperature from 150 to 200°C, the contrast between A‐O and F‐O conditions become more prominent. Specifically, at 200°C, the crosslinking density and tensile strength of FKM in A‐O decreased by 2.2 × 10−4 mol/cm3 and 2.5 MPa compared to that in F‐O, and the mass change reached to 3.8%, which might be due to the higher amount of oil medium by diffusion into the FKM matrix.

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