Study on aging state and life prediction of PTFE seals for nuclear power stations

doi:10.19491/j.issn.1001-9278.2022.10.015

Abstract

Abstract:

In this study， a high⁃temperature accelerated aging test was conducted for the polytetrafluoroethylene （PTFE） material used in nuclear power station at temperatures of 315， 300， and 285 ºC. The microstructure and thermal properties of the PTFE material were characterized using Fourier⁃transform infrared spectroscopy， SEM， and thermogravimetric （TG） analyzer. Two aging life prediction models were established through thermal aging using a TG method. The results indicated that PTFE exhibited an evident red shift in its infrared frequency together with some obvious hole marks appearing on its surface， suggesting a deterioration in thermal stability and mechanical property with the aging time. The life prediction model demonstrated that the life prediction results obtained from the TG method thermal aging method were consistent， and the error decreased with an increased in service temperature. This indicated that the TG method was reliable to calculate the service life of the PTFE material and very suitable for the evaluation of the PTFE material as a simple and convenient life prediction method.

Key words: polytetrafluoroethylene, thermal aging, life prediction

CLC Number:

TQ325.4

WU Kun, FAN Yaqin, SHEN Qian, MIAO Zhuang, ZHOU Cheng. Study on aging state and life prediction of PTFE seals for nuclear power stations[J]. China Plastics, 2022, 36(10): 98-103.

Figures/Tables 12

Fig.1. FTIR of samples with varied aging time

Fig.2. TG curves of samples with different aging time

Fig.3. Tensile strength and elongation at break of the materials at different aging time

Fig.4. SEM of PTFE at different aging time

Fig.5. Molecular chain structure of PTFE at different aging time

老化温度285 ℃		老化温度300 ℃		老化温度315 ℃
老化时间/d	拉伸强度/ MPa	老化时间/d	拉伸强度/ MPa	老化时间/d	拉伸强度/ MPa
0	34.5	0	34.5	0	34.5
70	30	20	29.3	9	27.4
140	27.2	40	27.1	18	24
210	24.6	60	23.9	27	23
280	20.9	80	21	36	20.5
350	16.1	100	17.2	45	17

Tab.1. Tensile strength of samples during accelerated aging

Fig.6. Life prediction curve

温度/℃	230	250	280
使用寿命/年	65.0	12.2	1.2

Tab.2. Working life at different working temperature

Fig.7. TG curves of FTFE at different heating rates

升温速率/℃·min^-1	5	10	15	20
T_{5 %}/℃	520.08	539.22	552.54	559.90

Tab.3. Temperature of 5 % thermogravimetric loss of FTFE at different heating rates

Fig.8. Linear relationship between lgβ of PTFE and（1/T） under 5 % thermal weight loss

温度/℃	热老化寿命预测/年	TG寿命预测/年
230	65	66
250	12.2	12.8
280	1.2	1.4

Tab. 4. Working life at different working temperature

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