热老化对恒定内压下PE管材性能的影响
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摘要
为了研究热老化对恒定内压作用下的PE管材结构和性能的影响,在80℃水浴环境中对聚乙烯管进行了长期压力测试,通过力学性能测试、热重试验、DSC测试以及衰弱全发射红外光谱试验,分析了老化过程中管材的结构和性能变化。结果表明,在老化过程中,随着老化时间的增加,PE管材抗氧化剂逐渐被消耗,2 200 h时,老化管材的氧化诱导期降低至原始管材的73. 1%;随着老化时间的延长,管材表面发生氧化,产生了羰基(—CO)与羟基(—OH)等含氧基团。热老化使PE分子链发生了以交联为主的化学反应,导致管材的热稳定性上升。结晶度增加、分子链交联以及管材表层氧化等,导致拉伸强度略有提升,而管材的断裂伸长率和冲击强度分别下降了27. 5%、28. 9%。
In order to study the effect of thermal ageing on the structure and properties of PE pipes under constant internal pressure,a long-term pressure test was carried out on the PE pipe at 80 ℃ water bath. The physical property and chemical structure before and after ageing were determined by mechanical properties test,thermogravimetric test,DSC test and attenuated total reflectance-Fourier transform infrared spectrum test( ATR/FTIR). In the ageing process,the antioxidants were gradually consumed with the increase of ageing time,and the oxidation induction time of the aged pipes was reduced to73. 1% until 2 200 h. The ATR/FTIR further showed that the crystallinity of PE increased. The surface of the pipe was oxidized and produced oxygen groups,such as carbonyl group( —CO) and hydroxyl group( —OH). The thermal ageing mainly caused crosslinking among the molecular chains,which increased the thermal stability of the material. The increase in crystallinity,cross-linking of molecular chains,even the oxidation of the surface layer caused the slight increase in tensile strength,while elongation at break and impact strength decreased by 27. 5% and 28. 9%,respectively.
In order to study the effect of thermal ageing on the structure and properties of PE pipes under constant internal pressure,a long-term pressure test was carried out on the PE pipe at 80 ℃ water bath. The physical property and chemical structure before and after ageing were determined by mechanical properties test,thermogravimetric test,DSC test and attenuated total reflectance-Fourier transform infrared spectrum test( ATR/FTIR). In the ageing process,the antioxidants were gradually consumed with the increase of ageing time,and the oxidation induction time of the aged pipes was reduced to73. 1% until 2 200 h. The ATR/FTIR further showed that the crystallinity of PE increased. The surface of the pipe was oxidized and produced oxygen groups,such as carbonyl group( —CO) and hydroxyl group( —OH). The thermal ageing mainly caused crosslinking among the molecular chains,which increased the thermal stability of the material. The increase in crystallinity,cross-linking of molecular chains,even the oxidation of the surface layer caused the slight increase in tensile strength,while elongation at break and impact strength decreased by 27. 5% and 28. 9%,respectively.
引文
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[3] IFWARSON M O. Life-time of polyethylene pipes under pressure and exposure to high temperatures[J]. Kunststoffe—German Plastics,1989,79(6):20-22.
[4] WEON J. Effects of thermal ageing on mechanical and thermal behaviors of linear low density polyethylene pipe[J]. Polymer Degradation and Stability,2010,95(1):14-20.
[5] HONG E M,LOWE D. Lifetime prediction of a blue PE100 water pipe[J]. Polymer Degradation and Stability,2008,93(8):1496-1503.
[6]许向青.氧化诱导期法评价聚烯烃管材的抗热氧稳定性[J].合成树脂及塑料,2002,19(5):32-36.
[7]田瑶君,秦军,熊玉竹,等. PE100材料的湿热老化性能及其寿命预测[J].塑料,2015,44(6):9-11.
[8]兰惠清,沙迪,孟涛,等.承压燃气聚乙烯管道热氧老化规律研究[J].天然气工业,2016,36(4):78-83.
[9] SHI X,WANG J,STAPF S,et al. Effects of thermo-oxidative ageing on chain mobility,phase composition,and mechanical behavior of high-density polyethylene[J]. Polymer Engineering&Science,2011,51(11):2171-2177.
[10] WEON J,CHOI K. Mechanical property behaviors of polyethylene pipe due to thermal-degradation[J]. Polymer Korea,2009,33(5):446-451.
[11] SPERLING L H. Introduction to Physical Polymer Science[M]. New York:Wiley,1986.
[12]高炜斌,徐亮成,淡宜.热氧老化对聚碳酸酯结构和性能的影响[J].塑料,2010,39(2):61-64.
[13] CORRALES T,CATALINA F,PEINADO C,et al. Photooxidative and thermaldegradation of polyethylenes:interrelationship by chemiluminescence,thermalgravimetric analysis and FTIR data[J].Journal of Photochemistry and Photobiology A:Chemistry,2002,147(3):213-224.
[14]申麦茹,铁文安,丁辉,等.燃气用聚乙烯管材的人工气候加速老化[J].工程塑料应用,2017,45(11):104-107.
[15] GEDDE U W,VIEBKE J,LEIJSTRM H,et al. Long-term properties of hot-water polyolefin pipes—a review[J]. Polymer Engineering and Science,1994,34(24):1773-1787.
[16] ABDELAAL F B,ROWE R K. Effect of high temperatures on antioxidant depletion from different HDPE geomembranes[J]. Geotextiles and Geomembranes,2014,42(4):284-301.
[17] HSUAN Y G,WONG W. Methodology to evaluate oxidation degradation of high-density polyethylene corrugated pipe resin[J]. Transportation Research Record:Journal of the Transportation Research Board,2010,2172(1):192-198.
[18] TIAN K,BENSON C H,TINJUM J M,et al. Antioxidant depletion and service life prediction for HDPE geomembranes exposed to low-level radioactive waste leachate[J]. Journal of Geotechnical and Geoenvironmental Engineering,2017,143(6):04017011.
[19] ZERBI G,GALLINO G,DEL FANTI N,et al. Structural depth profiling inpolyethylene films by multiple internal reflection infrared spectroscopy[J]. Polymer,1989,30(12):2324.
[20]代军,晏华,郭骏骏,等.结晶度对聚乙烯热氧老化特性的影响[J].材料研究学报,2017,31(1):41-48.
[21] KE Q Q,HUANG X Y,WEI P,et al. Thermal,mechanical,and dielectric behaviors of crosslinked linear low density polyethylene/polyolefin elastomers blends[J]. Journal of Applied Polymer Science,2007,104(3):1920-1927.