Influence of Silicone Rubber Coating on the Characteristics of Surface Streamer Discharge

A pollution flashover along an insulation surface—a catastrophic accident in electrical power system—threatens the safe and reliable operation of a power grid. Silicone rubber coatings are applied to the surfaces of other insulation materials in order to improve the pollution flashover voltage of the insulation structure. It is generally believed that the hydrophobicity of the silicone rubber coating is key to blocking the physical process of pollution flashover, which prevents the formation of continuously wet pollution areas. However, it is unclear whether silicone rubber coating can suppress the generation of pre-discharges such as corona discharge and streamer discharge. In this research, the influence of silicone rubber coating on the characteristics of surface streamer discharge was researched in-depth. The streamer ‘stability’ propagation fields of the polymer are lower than that of the polymer with silicone rubber coating. The velocities of the streamer propagation along the polymer are higher than those along the polymer with silicone rubber coating. This indicates that the surface properties of the polymer with the silicone rubber coating are less favorable for streamer propagation than those of the polymer.

Results of paint coating full-scale tests for coastal and ship structures in the tropical climate of Vietnam

Full-scale tests are widely used to reliably evaluation the service life of paint and varnish coatings by assessing changes of their protective and decorative properties. Four-year exposure program was carried out in the tropical marine climate in South Vietnam (Dam Bay climate station of the Tre island, Nha Trang) of alkyd, chlorinated rubber coatings on low carbon steel, as well as epoxy coatings of various thicknesses with zinc-rich primer, urethane and acrylic outer layers. The tests were conducted on the base of the existing standards in the field of paints and varnishes intended for coastal and ship structures and were accompanied by the data collection and analysis of the meteorological factors for the classification of the area according to the degree of corrosiveness of the atmosphere. The change in the decorative properties of paint coating was assessed by visual and instrumental methods. The protective efficiency of the coatings was assessed by the time of occurrence of the first local defects or complete destruction of coating layers. According to the results of the conducted field tests, it was found that paint coating combinations correspond to expected lifetime in tropical climate from 2 to 5 years. A typical group suitable for a given climate is a two-component epoxy paint with an acrylic topcoat. A zinc-containing primer is recommended as an anticorrosive undercoat.

Natural Rubber Composites for Paper Coating Applications

Natural rubbers are characterized by extremely high molecular weight that might be beneficial in the formation of a protective barrier layer on paper substrates, providing good cohesive properties but limited adhesion to the substrate. In parallel, the low glass transition temperature of natural rubber might give the opportunity for good sealability, in contrast with severe problems of tack. Therefore, natural rubbers can be good candidates to serve as an alternative ecological binder in paper coatings for water and grease barrier resistance. In order to tune the surface properties of the paper coating, the effect of different fillers in natural rubber coatings are evaluated on rheological, thermo–mechanical and surface properties. The fillers are selected according to common practice for the paper industry, including talc, kaolinite clay and a type of organic nanoparticle, which are all added in the range of 5 to 20 wt.-%. Depending on the selected natural rubber, the dispersibility range (i.e., dispersive and distributive mixing) of the fillers in the latex phase highly varies and filler/matrix interactions are the strongest for nanoparticle fillers. An optimum selection of viscosity range allows us to obtain homogeneous mixtures without the need of surface modification of the additives. After bar-coating natural rubber latex composites on paper substrates, the drying properties of the composite coatings are followed by spectroscopy, illustrating the influences of selected additives on the vulcanization process. In particular, the latter most efficiently improves in the presence of nanoparticle fillers and highly increases the coating hydrophobicity in parallel, reducing the adhesive tack surface properties, as predicted from calculated work of adhesion.

Study on the Anticondensation Characteristics of Liquid Silicone Rubber Temperature-Control Coatings

Metal cabinets such as switch cabinets and ring network cabinets have the advantages of small footprints and good protection for equipment and offer neat and orderly protection. They are widely used in power systems. In a hot and humid environment, condensation can easily cause equipment to age and even cause insulation failure. Therefore, research on reliable anticondensation methods is of great significance for the safe operation of power equipment. In this study, phase change capsules with phase transition temperatures of 22 and 32 °C were used as fillers and liquid silicone rubber was used as a matrix to prepare liquid silicone rubber composites filled with phase change capsules for a temperature-control coating. Studies have shown that liquid silicone rubber coatings containing phase change capsules can significantly enhance the anticondensation performance of metal cabinets. By using a temperature-control coating on the surface where the cabinet experiences condensation, the temperature difference between the surface and the dew point is reduced, thereby slowing down the condensation rate and even preventing condensation.