Quantitative analysis of changes in antioxidant in crosslinked polyethylene (XLPE) cable insulation material exposed to heat and gamma radiation

Abstract

Quantitative analysis of the antioxidant poly(1,2-dihydro-2,2,4-trimethylquinoline) (pTMQ) was conducted on pristine, thermally-aged, and gamma radiation-aged commercial cross-linked polyethylene-(XLPE-)based cable insulation material aged at temperatures 60, 90, and 115 °C, with gamma radiation exposure dose rates of 0, 120, 300, and 540 Gy/h for 15 days. The quantification of antioxidant was performed using pyrolysis gas chromatography-mass spectrometry (Py-GCMS). Oxidation induction time (OIT) was measured using differential scanning calorimetry (DSC) and correlation was made between the quantified depletion of antioxidant and measured OIT. It was observed that, in the case of isothermal aging, the quantity of antioxidant and OIT decreased with increasing gamma radiation dose. In the case of samples exposed to the same gamma radiation dose, the quantity of antioxidant and OIT were observed to decrease with increasing aging temperature. Depletion in the quantity of antioxidant relative to that in the pristine material ranged from 7 to 93% for differently aged samples. The measured decline in OIT ranged from 0 to 80%. Change in the quantity of antioxidant in the material was observed to follow the same trend as the change in OIT when the samples were aged under various conditions. The observations are explained in terms of the reaction between the antioxidant and free radicals created during exposure of the samples to thermal and gamma radiation. AbstractQuantitative analysis of the antioxidant poly(1,2-dihydro-2,2,4-trimethylquinoline) (pTMQ) was conducted on pristine, thermally-aged, and gamma radiation-aged commercial cross-linked polyethylene-(XLPE-)based cable insulation material aged at temperatures 60, 90, and 115 °C, with gamma radiation exposure dose rates of 0, 120, 300, and 540 Gy/h for 15 days. The quantification of antioxidant was performed using pyrolysis gas chromatography-mass spectrometry (Py-GCMS). Oxidation induction time (OIT) was measured using differential scanning calorimetry (DSC) and correlation was made between the quantified depletion of antioxidant and measured OIT. It was observed that, in the case of isothermal aging, the quantity of antioxidant and OIT decreased with increasing gamma radiation dose. In the case of samples exposed to the same gamma radiation dose, the quantity of antioxidant and OIT were observed to decrease with increasing aging temperature. Depletion in the quantity of antioxidant relative to that in the pristine material ranged from 7 to 93 % for differently aged samples. The measured decline in OIT ranged from 0 to 80 %. Change in the quantity of antioxidant in the material was observed to follow the same trend as the change in OIT when the samples were aged under various conditions, with a correlation coefficient of 0.82. The observations are explained in terms of the reaction between the antioxidant and free radicals created during exposure of the samples to thermal and gamma radiation.

Influence of Gamma Irradiation on Electric Cables Models: Study of Additive Effects by Mid-Infrared Spectroscopy

“…Consistent with the literature [ 7 ], the high antioxidant concentration in the samples results in an increase in the OIT values and, therefore, the samples containing the Irganox 1076 antioxidant show the highest OIT values. For stabilized polymers, OIT measurements can be used to give an assessment of the level of stabilization of the material, as OIT is the time required to consume all the stabilizers (especially antioxidants additives).…”

“…The formation of unsaturated groups is monotonic with the absorbed dose. The irradiation generates trans-vinylene groups, slightly degrades the vinyl end groups, and does not alter the vinylidene groups [ 6 , 7 , 11 ].…”

“…This is the scope of the European Union (EU) project called TeaM Cables which aims at developing cable ageing models and algorithms, based on multi-scale studies of their degradation under different conditions: gamma irradiation and/or thermal ageing [ 4 ]. The thermal degradation [ 5 ] and gamma radiation [ 6 , 7 ] of polyethylene has been intensively studied. In this work, only degradation under gamma irradiation is studied, all experiments taking place at room temperature.…”

Broadband FIR absorption spectra of low‐density polyethylene sheets containing six different antioxidants and estimation of their contents by chemometric analysis

“…However, if organic polymers are used under a harsh environment or they are processed at high temperatures for a long time, degradation resulting from oxidation would occur [4,5]. In many cases, antioxidants are added to polymeric insulating materials to suppress such oxidative degradation [6][7][8][9][10]. Here, a problem for users of polymeric insulation is that the details of antioxidant added to the polymer are seldom disclosed.…”

Electrical conductivity of waxes as model systems for polyethylene: Role of water

“…In terms of the values in Table (where the sum total of all fractions adds up to 100 wt %) this implies a minimum detectable impurity concentration of ~0.02 wt % or 200 ppm. In contrast, a commercial PE contains antioxidants at typical concentrations of 0.05–1 wt % and other additives, such as flame retardants, may be present in even greater proportions . Therefore, compared to commercial PE, PW is a very clean system indeed.…”