Aging evaluation of polyethylene gas pipes under high temperature and inner pressure environment

doi:10.19491/j.issn.1001-9278.2022.10.013

Abstract

Abstract:

The polyethylene gas pipe samples were aged in a water bath at 80 ºC and 1.1 MPa for 0， 165， 500， and 1 000 h. The isothermal oxidation induction time （OIT）， thermal decomposition temperature （T_s）， functional group composition， and elongation at break （ε） of each aged specimens were investigated using DSC， TG， FTIR， and tensile measurement. The change rule in the aging performance law of polyethylene gas pipes was analyzed under high temperature and inner pressure environment. The results indicated that the polyethylene gas pipes presented a gradual decrease in isothermal OIT， T_s， and ε with an increase in aging degree. The aging rate of the inner wall was significantly higher than that of the outer wall. FTIR analysis results indicated that there were two characteristic absorption peaks at 1 720 cm^-1 and 3 400 cm^-1 corresponding to C=O and O—H vibration， respectively， in the functional group diagram of polyethylene pipe material with an increase in aging time. This further confirmed the introduction of oxidation reaction products into the molecular chain of polyethylene pipes.

Key words: polyethylene, aging performance, oxidation induction time, thermal decomposition temperature, functional group, elongation at break

CLC Number:

TQ325.1⁺2

WANG Zhigang, YANG Bo, ZENG Chen, LI Zhi, DENG Jianyi. Aging evaluation of polyethylene gas pipes under high temperature and inner pressure environment[J]. China Plastics, 2022, 36(10): 84-89.

Figures/Tables 14

Fig.1. The thermal oxygen aging scheme of PE material

样品编号	牌号	参数	试验参数	老化时间/h
1^#	HD⁃PE100⁃P6006	密度ρ为959 g/cm³ 熔体流动速率为0.22 g /10 min 等温OIT>20 min 炭黑含量为2.25 %	80 ℃、1.1 MPa、水	0
2^#			80 ℃、1.1 MPa、水	165
3^#			80 ℃、1.1 MPa、水	500
4^#			80 ℃、1.1 MPa、水	1 000

Tab.1. The aging test condition

Fig.2. The thermal oxygen aging test system diagram and prepared PE pipe samples

Fig.3. DSC curves of inner and outer wall samples of PE pipe with different aging time

样品编号	老化时间/h	平均等温 $O I T ¯$ /min
样品编号	老化时间/h	管外壁	管内壁
1^#	0	118.05	116.49
2^#	165	109.41	105.57
3^#	500	103.21	100.89
4^#	1 000	101.38	95.58

样品编号	老化时间/h	平均等温 $O I T ¯$ /min
样品编号	老化时间/h	管外壁	管内壁
1^#	0	118.05	116.49
2^#	165	109.41	105.57
3^#	500	103.21	100.89
4^#	1 000	101.38	95.58

Tab. 2. The average isothermal OIT¯ results of inner and outer wall samples of PE pipe with different aging time

Fig.4. OIT change trend of inner and outer wall samples of PE pipe with different aging time

Fig.5. Ts curves of outer wall samples of PE pipe with different aging time

样品编号	试验参数	老化时间/h	$T s ¯$ /℃
样品编号	试验参数	老化时间/h	管外壁	管内壁
1^#	80 ℃，1.1 MPa，水	0	479.15	479.10
2^#		165	479.17	479.05
3^#		500	476.00	475.67
4^#		1 000	475.83	473.33

样品编号	试验参数	老化时间/h	$T s ¯$ /℃
样品编号	试验参数	老化时间/h	管外壁	管内壁
1^#	80 ℃，1.1 MPa，水	0	479.15	479.10
2^#		165	479.17	479.05
3^#		500	476.00	475.67
4^#		1 000	475.83	473.33

Tab.3. The average thermal decomposition temperature Ts¯ results of inner and outer walls of PE pipes with different aging time

Fig.6. Ts change trend of inner and outer walls of PE pipe with different aging time

Fig.7. FTIR spectra of PE pipe samples with different aging time

样品编号	老化时间/h	A_{2 900}		A_{1 720}		CI/%
样品编号	老化时间/h	管外壁	管内壁	管外壁	管内壁	管外壁	管内壁
1^#	0	3 683.76	3 611.52	18.35	15.68	0.49	0.43
2^#	165	3 614.86	3 524.69	35.76	42.05	0.99	1.19
3^#	500	3 633.41	4 632.68	54.33	76.98	1.49	1.66
4^#	1 000	3 647.31	3 645.63	82.60	112.56	2.26	3.09

Tab.4. The carbonyl index CI results of inner and outer walls of PE pipe with different aging time

Fig.8. The stress⁃strain curves of PE pipe samples with different aging time

样品编号	老化时间/h	断裂伸长率/%	是否合格
1^#	0	596.6	是
2^#	165	559.72	是
3^#	500	551.00	是
4^#	1 000	473.09	是

Tab.5. The elongation at break of PE pipe samples with different aging time

Fig.9. The elongation at break change trend of PE pipe samples with different aging time

References 7

1	Dörner G， Lang R W. Influence of various stabilizer systems on the ageing behavior of PE⁃MD⁃I. Hot⁃water ageing of compression molded plaques［J］. Polymer Degradation & Stability， 1998， 62（3）：421⁃430.
2	Maria R， Rode K， Schuster T， et al. Ageing study of different types of long⁃term pressure tested PE pipes by IR⁃microscopy［J］. Polymer， 2015， 61：131⁃139.
3	Viebke J， Gedde U W. Antioxidant diffusion in polyethylene hot⁃water pipes［J］. Polymer Engineering & Science， 1997， 37（5）：896⁃911.
4	毕大芝，张勇，张隐西. 高密度聚乙烯热烘箱老化中的新现象［J］. 合成橡胶工业， 2004， 27（1）：47.
	BI D Z， ZHANG Y， ZHANG Y X. New phenomenon of HDPE aging in hot oven［J］.China Synthetic Rubber Industry， 2004， 27（1）：47.
5	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.
	LAN H Q， SHA D， MENG T，et al. Study on thermal oxygen aging law of pressure gas polyethylene pipe［J］.Natural Gas Industry B， 2016， 36（4）：78⁃83.
6	代军，晏华，郭骏骏，等. 不同类型聚乙烯光氧老化特性比较研究［J］. 工程塑料应用， 2016， 44（8）：88⁃92.
	DAI J， YAN H， GUO J J，et al.Comparative study on photooxidative aging characteristics of different types of polyethylene［J］. Engineering Plastics Application，2016， 44（8）：88⁃92.
7	刘亚平，李晖，魏绪玲. 高密度聚乙烯户外自然老化的力学性能研究［J］. 山东化工， 2007， 36（8）：5⁃7.
	LIU Y J， LI H， WEI Z L.Study on mechanical properties of high density polyethylene during outdoor natural aging［J］.Shandong Chemical Industry， 2007， 36（8）：5⁃7.

[1]	YANG Bo, YANG Zhen, ZENG Chen, WANG Zhigang, ZHAI Wei, CAO Fuxiang. Lifetime prediction of polyethylene pipe based on cyclic load [J]. China Plastics, 2022, 36(9): 63-69.
[2]	LI Yan, TANG Xiaoxu, ZHANG Weijie, HUANG Ruipeng, ZHANG Shan. Research progress in evaluation of slow crack growth resistance of polyethylene pipes based on strain hardening modulus [J]. China Plastics, 2022, 36(9): 148-159.
[3]	YU Darong, XIN Yong. Research progress in modification of ultrahigh molecular weight polyethylene [J]. China Plastics, 2022, 36(8): 135-145.
[4]	LI Guo, ZHU Huihao, MA Yulu, WANG Yu, JI Huajian, XIE Linsheng. Preparation and properties of microporous breathable films with high thermal conductivity [J]. China Plastics, 2022, 36(7): 14-20.
[5]	WU Xiongjie, ZHU Dongbo, SUN Jiangbo, GAO Longmei, CHU Yu, CHENG Jinsong, XIE Aidi. Study on application performance of polyethylene/CaSO₄ nanoparticle composite flexible packaging [J]. China Plastics, 2022, 36(6): 10-15.
[6]	LEI Yujie, CHEN Minghuan, WANG Jieyao, CHEN Wangzhi, LI Lei. Cross⁃linked foaming process and performance of recycled polyethylene [J]. China Plastics, 2022, 36(6): 124-129.
[7]	ZHU Jingyun, YI Huijun, YAN Wei, LI Dawei. Research and development of polyethylene special materials for compound films [J]. China Plastics, 2022, 36(6): 77-80.
[8]	XIA Yunxia, LI Lei, LUO Zhangsheng, ZHU Qianqin, HE Lijun. Preparation and properties of recycled polyethylene non⁃woven fabrics based on flash evaporation [J]. China Plastics, 2022, 36(5): 14-18.
[9]	WANG Ke, LONG Chunguang. Mechanical and tribological properties of ultra⁃high molecular weight polyethylene/sepiolite fiber composites [J]. China Plastics, 2022, 36(5): 19-23.
[10]	WEN Yuan, MAO Xianpeng, XU Kejie. Effect of sample thickness on tensile properties of polyethylene [J]. China Plastics, 2022, 36(4): 43-46.
[11]	XU Rongxia, WEI Gang, WEI Lilan, WU Jiecui, JIANG Yujiang. Friction and wear properties of PE⁃UHMW modified with nano⁃SiO₂ and PA6 [J]. China Plastics, 2022, 36(4): 47-52.
[12]	LIU Qiang, LU Yahong, WU Hui, MA Yuhao, ZHANG Yupeng, SUN Wenxiao, ZHANG Hong. Microbial degradation of polyethylene plastics [J]. China Plastics, 2022, 36(3): 120-126.
[13]	HENG Yue, XUE Nanxiang, CHEN Zhuangxin, LEI Caihong, XU Ruijie. Dynamic rheological behavior and compatibility of polyethylene/paraffin oil blends [J]. China Plastics, 2022, 36(2): 13-18.
[14]	ZHANG Xuemin, HOU Lin, FENG Jinmao, YAO Zhongliang, ZHONG Mingqiang. Study on natural aging behavior of buried polyethylene water supply pipeline in service [J]. China Plastics, 2022, 36(2): 49-55.
[15]	LI Bo, GONG Jun, JIN Xueyi, MENG Xiaoyu. Effect of carbon nanotube modification method on properties of polyamide 11 [J]. China Plastics, 2022, 36(2): 61-66.