Thermal aging of cross-linked polyethylene

Boukezzi, Larbi; Nedjar, Mohammed; Mokhnache, L.; Lallouani, Mohammed; Boubakeur, A.

doi:10.3166/acsm.31.561-569

Cited by 33 publications

(22 citation statements)

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“…The boxes were sheltered from UV radiation, but subject to normal changes in temperature and humidity as ambient conditions varied in the storage room. This ''unassisted'' aging contrasts with most previous work on polymers, where aging effects are accelerated with the aid of temperature, UV radiation, or chemicals (Clough et al, '96;El Shafee, 2003;Vlasveld et al, 2005;Boukezzi et al, 2006). However, natural aging may be a useful framework for understanding the durability of fibers and causes of degradation.…”

Section: Major Ampullate Dragline Silkmentioning

confidence: 42%

Spider silk aging: initial improvement in a high performance material followed by slow degradation

2008

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Spider silk possesses a unique combination of high tensile strength and elasticity resulting in extraordinarily tough fibers, compared with the best synthetic materials. However, the potential application of spider silk and biomimetic fibers depends upon retention of their high performance under a variety of conditions. Here, we report on changes in the mechanical properties of dragline and capture silk fibers from several spider species over periods up to 4 years of benign aging. We find an improvement in mechanical performance of silk fibers during the first year of aging. Fibers rapidly decrease in diameter, suggesting an increase in structural alignment and organization of molecules. One-year old silk also is stiffer and has higher stress at yield than fresh silk, whereas breaking force, elasticity, and toughness either improve or are unaffected by early aging. However, 4-year old silk shows signs of degradation as the breaking load, elasticity, and toughness are all lower than in fresh silk. Aging, however, does not reduce the tensile strength of silk. These data suggest initially rapid reorganization and tighter packaging of molecules within the fiber, followed by longer-term decomposition. We hypothesize that possibly the breakdown of amino acids via emission of ammonia gas, as is seen in long-term aging of museum silkworm fabrics, may contribute. Degradation of spider silk under benign conditions may be a concern for efforts to construct and utilize biomimetic silk analogs. However, our findings suggest an initial improvement in mechanical performance and that even old spider silk still retains impressive mechanical performance.

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Section: Major Ampullate Dragline Silkmentioning

confidence: 42%

Spider silk aging: initial improvement in a high performance material followed by slow degradation

2008

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“…By extrapolation of the thermal endurance graph to life length of 20000 hours [11,24], the index temperature is deduced to be 78.82°C (Table 6). The obtained value is slightly higher than that found in literature [25] via conventional method. In Figure 9, we have presented the lifetime endurance of the insulation, where we have reported the variation of aging time (in logarithmic) as a function of the reciprocal of absolute temperature [24].…”

Section: Thermal Endurence Of Xlpecontrasting

confidence: 53%

A Fuzzy Logic Approach to Model and Predict HV Cable Insulation Behaviour under Thermal Aging

Bessissa¹,

Boukezzi

Mahi³

2014

APH

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“…[23][24][25] With the rise of aging temperature, the molecular movement of the polymer chains intensifies, the viscosity reduces and the conductivity increases significantly. Meanwhile, the antioxidant is gradually consumed and the cross-linking degree decreases, then ε and ε increase as a whole.…”

Section: B Test Results and Analysis Of Thermal Aging In The Range Omentioning

confidence: 99%

“…Meanwhile, the antioxidant is gradually consumed and the cross-linking degree decreases, then ε and ε increase as a whole. [23][24][25][26] When the electric field frequency is very low, the carriers in XLPE would accumulate at the interface and in the defects and form the interfacial polarization. In addition, there are many factors influencing the XLPE dielectric constant, such as the steering of the molecular chain, the fracture of the macromolecular chain, the dipole turn formed by oxidation, and the ion displacement polarization caused by the ionization of impurities, which are generated by the alternating electric field.…”

Section: B Test Results and Analysis Of Thermal Aging In The Range Omentioning

confidence: 99%

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Influence of thermal aging on AC leakage current in XLPE insulation

et al. 2018

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Research on aging parameters of XLPE cable based on isothermal relaxation current AIP Advances 8, 075323 (2018) Cross-linked polyethylene (XLPE) has been widely used as cable insulation material because of its excellent dielectric properties, thermal stability and solvent resistance. To understand the influence of thermal aging on AC leakage current in XLPE insulation, all XLPE specimens were aged in oven in temperature range from 120 • C to 150 • C, and a series of tests were conducted on these XLPE specimens in different aging stages to measure the characteristic parameters, such as complex permittivity, leakage current and complex dielectric modulus. In the experiments, the effects of thermal aging, temperature and frequency on the AC leakage current in XLPE insulation were studied by analyzing complex dielectric constant and dielectric relaxation modulus spectrum, the change of relaxation peak and activation energy. It has been found that the active part of leakage current increases sharply with the increase of aging degree, and the test temperature and frequency have an influence on AC leakage current but the influence of test temperature is mainly reflected in the low frequency region. In addition, it has been shown by the experiments that the reactive part of leakage current exhibits a strong frequency dependent characteristic in the testing frequency range from 10 -2 Hz to 10 5 Hz, but the influence of test temperature and thermal aging on it is relatively small. © 2018 Author (s)

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Thermal aging of cross-linked polyethylene

Cited by 33 publications

References 0 publications

Spider silk aging: initial improvement in a high performance material followed by slow degradation

Spider silk aging: initial improvement in a high performance material followed by slow degradation

A Fuzzy Logic Approach to Model and Predict HV Cable Insulation Behaviour under Thermal Aging

Influence of thermal aging on AC leakage current in XLPE insulation

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