Surface modification of XLPE films by CF4 DBD for dielectric properties

Abstract

Cross-linked polyethylene (XLPE) is often manufactured as pipe, film and foam products and used as electric insulation material. To improve the dielectric properties of XLPE film, CF4 dielectric barrier discharge (DBD) is applied as a surface modification method. The surface of XLPE film was modified at the low pressure of 1 kPa with different treatment time (15s, 30s, 60s, 120s, 240s and 480s). Electrical and optical characteristics are observed during DBD process, including applied voltage, measured current, photograph and emission spectra. Then, the surface properties, which are hydrophobicity, chemical composition, surface morphology, trap depth, dielectric loss and AC breakdown voltage, have been measured or observed by water contact angle test, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), isothermal relaxation current (IRC), frequency domain spectroscopy (FDS) and withstand voltage test. After the surface modification, the water contact angle, trap depth and breakdown voltage increase first and then decrease with treatment time extending. Meanwhile, the dielectric loss has an opposite trend, which represents better dielectric properties. The reason is that fluorine can reduce the surface energy, which can significantly influence the water contact angle. Better hydrophobicity can restrain the accumulation of outside pollution on the surface. Moreover, fluorine has strong electronegativity, so amorphous crystalline and impurities interface trap depth become deeper and the dielectric loss becomes lower. Therefore, appropriate DBD treatment conditions can apparently improve XLPE dielectric properties.

Review of interface tailoring techniques and applications to improve insulation performance

“…For example, a nanostructured PTFE layer was formed onto cellulose paper using magnetron sputtering, and thereby, various properties of oilpaper insulation were improved [8]. In another study, CF 4 DBD was used as a surface modification method to improve the dielectric properties of cross-linked polyethylene film, and breakdown strength and dielectric loss were improved [84]. To clarify the underlying mechanisms, the charge injection characteristics of PE and PTFE oligomers were investigated using first-principle calculations, and the results indicated that the charge injection barrier is higher at the metal/PTFE interface in the case of chemisorption [85].…”

“…For this reason, several insulation problems faced with typical power equipment such as capacitors and cables can be addressed by increasing the injection barrier. For instance, the space charge density in polymers can be reduced by increasing the injection barrier, which lowers the distortion of electric field distribution in the power cable and thereby increases breakdown strength and reduces the possibility of electrical ageing–induced insulation failure [84]. In addition, electrical conduction loss in the energy‐storage dielectric can be effectively reduced, which improves energy density and charge–discharge efficiency, especially under elevated temperature.…”

Effect of CF4 additive on dynamic surface charge deposited on dielectric by helium atmospheric pressure plasma jet

“…They found that APPJ modification can achieve a better uniformity in comparison to the more violent reaction of DBD method. Surely, there are a variety of reactor structures for the generation of fluorocarbon plasma [17][18][19]. CF 4 is a highly electronegative gas that can absorb free electrons during the discharge process to affect the ionization process of APPJs.…”

Improved Insulating Properties of Polymer Dielectric by Constructing Interfacial Composite Coatings

“…Considering that most space charge accumulation takes place at the interface between electrodes and polymers, it is therefore more effective to alleviate space charge accumulation by manipulating the trap distribution at the interface rather than doping nanoparticles into the polymer matrix. Currently, the prevailing techniques employed for interface tailoring encompass primarily surface fluorination treatment [ 28 , 29 ], magnetron sputtering [ 30 , 31 ], plasma surface modification [ 32 , 33 ], and chemical vapor deposition [ 34 , 35 , 36 ], among others. However, it is noteworthy that these methods typically necessitate the utilization of intricate experimental apparatus.…”