Aging behaviors of polyethylene gas pipeline under high temperature and external load

doi:10.19491/j.issn.1001-9278.2025.09.012

Abstract

Abstract:

In this study， the thermal oxidative aging behavior of polyethylene gas pipelines was investigated under combined high⁃temperature and mechanical loading conditions. A specialized experimental apparatus was developed to simulate aging under these operational stresses. The effects of external loading on mechanical properties， microstructure， and thermal characteristics were systematically evaluated using tensile testing， scanning electron microscopy， Fourier⁃transform infrared spectroscopy， and differential scanning calorimetry. Results demonstrated that prolonged high⁃temperature exposure led to decreased elongation at break and reduced oxidation induction time， while increasing both carbonyl index and material crystallinity. Notably， applied external loads significantly accelerated the aging process. At a 1 000 N load， the aging rate increased by factors of 1.8 （elongation）， 1.17 （carbonyl index）， and 1.3 （oxidation induction time） compared to unloaded samples. These findings quantitatively established the synergistic degradation effects of thermal and mechanical stresses on pipeline polyethylene， providing critical insights for material service life prediction and maintenance strategies.

Key words: gas pipelines, high?density polyethylene, external load, thermal?oxidative aging, aging rate

CLC Number:

TQ325.1

XU Feng, LI Yingjie, YANG Juyi, LI Xuan, CHU Chenglin. Aging behaviors of polyethylene gas pipeline under high temperature and external load[J]. China Plastics, 2025, 39(9): 75-80.

Figures/Tables 12

Fig.1. Illustration of thermal oxygen aging experimental device with external load and the selected location of the samples

Fig.2. The stress⁃strain curves of PE⁃HD samples with different aging times at 80℃ under different external loads

老化时间/h	屈服强度/MPa		断裂伸长率/%
老化时间/h	0 N	1 000 N	0 N	1 000 N
0	23.1±1.5	23.1±1.5	512±20	512±20
168	23.5±1.8	21.8±1.5	480±18	448±16
336	23.2±2.1	22.9±2.3	437±19	367±21
720	22.8±1.1	22.8±2.4	370±15	283±18

Tab.1. The yield strength and elongation of PE⁃HD samples after different aging processes

Fig.3. Tensile fracture morphology of PE⁃HD samples aged at 80 ℃ for 720 hours under different external loads

Fig.4. Infrared spectra of PE⁃HD samples aged at 80 ℃ under different external loads

Fig. 5. Carbonyl index of PE⁃HD samples after different aging processes

Fig.6. DSC curves of PE⁃HD samples aged at 80 ℃ under different external loads

老化时间/h	结晶度/%
老化时间/h	0 N	1 000 N
0	51.8	51.8
168	53.2	53.1
336	53.6	54.2
720	56.9	57.3

Tab.2. Crystallinity of PE⁃HD samples after different aging processes

Fig.7. Ratio of oxidation induction time to initial oxidation induction time of PE⁃HD samples after different aging processes

Fig.8. Mechanism of thermal⁃oxidative aging of PE⁃HD samples

Fig.9. Relationship between performance change indicators and aging time of PE⁃HD samples

性能指标	老化速率/h^-1
性能指标	0 N	1 000 N
断裂伸长率	4.57×10^-4	8.32×10^-4
羰基指数	2×10^-3	2.34×10^-3
氧化诱导期	5.2×10^-4	6.8×10^-4

Tab.3. Aging rates of PE⁃HD samples calculated by different performance indicators

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