Performance degradation of HTPO internal penetration pipe under oil transportation conditions
In order to investigate the performance degradation of high temperature resistant polyolefin(HTPO)internal penetration pipe under the oil transmission conditions,kerosene medium was used to replicate the operational conditions of oil transmission.Through an examination of the fluctuations in mass,density,structural composition,micro-morphology,thermal stability and mechanical properties of the pipelines under varying temperatures(20~80℃)and immersion durations(0~7 weeks),it is found that:When subjecting HTPO pipes to heating in the air environment,predominant thermal oxidation takes place.With the increase of temperature,there are no obvious changes in the mass and density,the thermal stability slightly decreases,the absorption peaks of carbon-oxygen groups are enhanced,the minor surface cracks appear on material surface,and yield strength and modulus of elasticity decrease by 8.15%and 13.12%,respectively.When the pipes are immersed at 20℃ for one week,due to the swelling effect of the kerosene medium,C=C swelling absorption peak and C=O expansion vibration peak appear,the surface of HTPO exhibits grooves,and its yield strength and modulus of elasticity experience reductions of 3.11%and 7.93%,respectively.With the increase of temperature and immersion time,the extent of oxidative degradation of the pipe rises,and kerosene swelling intensifies.After subjecting the sample to 80℃ for seven weeks,a notable 10.4%increase in sample mass is observed.Additionally,the intensity of the C=C peak and C=O peak is enhanced,along with the appearance of an"etching"phenomenon on the material surface.The yield strength and elastic modulus decrease by 38.75%and 75.51%,respectively,and the thermal stability significantly declines.