With the widespread use of polyethylene(PE)materials in gas pipelines,the problem related to the aging of these pipes has attracted increasing attention.Especially under complex environmental conditions involving temp...With the widespread use of polyethylene(PE)materials in gas pipelines,the problem related to the aging of these pipes has attracted increasing attention.Especially under complex environmental conditions involving temperature,humidity,and pressure changes,PE pipes are prone to oxidative degradation,which adversely affects their performance and service life.This study investigates the aging behavior of PE pipes used for gas transport under the combined effects of temperature(ranging from 80℃to 110℃)and pressure(0,0.1,0.2,and 0.3 MPa).By assessing the characteristics and thermal stability of the aged pipes,relevant efforts are provided to explore the performance variations during the aging process and develop methods for evaluating thermal stability.The results indicate that an increase in aging factors,specifically temperature and pressure,significantly reduces theMeltMass Flow Rate(MFR)of polyethylene pipes,suggesting a decline in the material’s flowability during the aging process.Oxidative Induction Time(OIT)tests show that with increasing temperature and pressure,the oxidative induction time of the aged polyethylene pipes progressively shortens,indicating a significant reduction in the material’s oxidative stability.The application of the Arrhenius equation further demonstrates that the aging reaction rate of polyethylene pipes in high-temperature environments is closely related to both temperature and activation energy,thereby laying the foundation of a new approach for the development of an initial model that can reflect the microscopic behavior of polyethylene pipes in aging environments.展开更多
The service life of a polyolefin product depends to large extent on the type and amount of the antioxidants added. During the manufacturing,storage and use of the product the antioxidants are depleted by physical proc...The service life of a polyolefin product depends to large extent on the type and amount of the antioxidants added. During the manufacturing,storage and use of the product the antioxidants are depleted by physical processes and chemical degradation,and this impairs its long-term performance.The initial and in-use oxidation stability is often characterized and monitored by the measurement of the oxidative induction time(OIT),and service life predictions are based on the rate of decrease of the OIT value.To study the correlation between the OIT value and the actual antioxidant concentration,eight random arrays of high-impact polypropylene(PP)strands stabilized using six different antioxidant packages(composed of Irgafos 168,Irganox 1010 and 1330,Chimassorb 944)were immersed in hot water(80℃and 90℃)and oven aged in air (80℃)for more than two years,and the change of OIT values and antioxidant concentrations was measured.For phosphitic and phenolic stabilizers water immersion is generally a more critical aging condition than oven aging in air,while for the hindered amine stabilizers(HAS)the opposite was observed.As expected,a linear correlation between OIT values and concentrations was found for the'classical'package of phosphitic and phenolic stabilizers.In the case of Irganox 1330,the change of the OIT values during aging was considerably slower than the change of concentration.Even when zero concentration was reached according to the vanishing peak height in the chromatogram,a considerable OIT value was still measurable.This may be due to unidentified degradation products of Irganox 1330 which still act as antioxidants in the long run.Addition of HAS(Chimassorb 944)seems to enhance the initial OIT of stabilized phenolic samples and the long-term effectiveness of the phenolic stabilization under air oven aging conditions.However,the marked long-term effectiveness of the HAS itself and the slow change with time of the concentration were not detectable by OIT measurements above the PP melting point of about 170℃.展开更多
基金supported by the Sponsored by Natural Science Foundation of Xinjiang Uygur Autonomous Region(no.2022D01C389)the Xinjiang University Doctoral Start-up Foundation(no.620321029)the Science and Technology Planning Project of State Administration for Market Regulation(no.2022MK201).
文摘With the widespread use of polyethylene(PE)materials in gas pipelines,the problem related to the aging of these pipes has attracted increasing attention.Especially under complex environmental conditions involving temperature,humidity,and pressure changes,PE pipes are prone to oxidative degradation,which adversely affects their performance and service life.This study investigates the aging behavior of PE pipes used for gas transport under the combined effects of temperature(ranging from 80℃to 110℃)and pressure(0,0.1,0.2,and 0.3 MPa).By assessing the characteristics and thermal stability of the aged pipes,relevant efforts are provided to explore the performance variations during the aging process and develop methods for evaluating thermal stability.The results indicate that an increase in aging factors,specifically temperature and pressure,significantly reduces theMeltMass Flow Rate(MFR)of polyethylene pipes,suggesting a decline in the material’s flowability during the aging process.Oxidative Induction Time(OIT)tests show that with increasing temperature and pressure,the oxidative induction time of the aged polyethylene pipes progressively shortens,indicating a significant reduction in the material’s oxidative stability.The application of the Arrhenius equation further demonstrates that the aging reaction rate of polyethylene pipes in high-temperature environments is closely related to both temperature and activation energy,thereby laying the foundation of a new approach for the development of an initial model that can reflect the microscopic behavior of polyethylene pipes in aging environments.
文摘The service life of a polyolefin product depends to large extent on the type and amount of the antioxidants added. During the manufacturing,storage and use of the product the antioxidants are depleted by physical processes and chemical degradation,and this impairs its long-term performance.The initial and in-use oxidation stability is often characterized and monitored by the measurement of the oxidative induction time(OIT),and service life predictions are based on the rate of decrease of the OIT value.To study the correlation between the OIT value and the actual antioxidant concentration,eight random arrays of high-impact polypropylene(PP)strands stabilized using six different antioxidant packages(composed of Irgafos 168,Irganox 1010 and 1330,Chimassorb 944)were immersed in hot water(80℃and 90℃)and oven aged in air (80℃)for more than two years,and the change of OIT values and antioxidant concentrations was measured.For phosphitic and phenolic stabilizers water immersion is generally a more critical aging condition than oven aging in air,while for the hindered amine stabilizers(HAS)the opposite was observed.As expected,a linear correlation between OIT values and concentrations was found for the'classical'package of phosphitic and phenolic stabilizers.In the case of Irganox 1330,the change of the OIT values during aging was considerably slower than the change of concentration.Even when zero concentration was reached according to the vanishing peak height in the chromatogram,a considerable OIT value was still measurable.This may be due to unidentified degradation products of Irganox 1330 which still act as antioxidants in the long run.Addition of HAS(Chimassorb 944)seems to enhance the initial OIT of stabilized phenolic samples and the long-term effectiveness of the phenolic stabilization under air oven aging conditions.However,the marked long-term effectiveness of the HAS itself and the slow change with time of the concentration were not detectable by OIT measurements above the PP melting point of about 170℃.
