RESUMEN
Polymeric composite insulators consisting of core fiber reinforced polymer insulators covered with polydimethylsiloxane (PDMS) housing are now replacing conventional ceramic insulators especially for high-outdoor power transmission lines due to some specific advantages. Unlike ceramics, polymers have relatively shorter life. Outdoor insulators experience different electrical, mechanical, chemical, and thermal stresses during service. The long-term service performance of these insulators and their service life estimation is an important issue, but it is complicated and time-consuming. The objective of the present investigation is to check the rate of property deterioration during service and to find the approximate lifetime. Working insulators with different ages were collected from service, and the changes in mechanical and electrical properties and hydrophobicity of the PDMS cover against aging time were measured. The service life estimated from the change in mechanical properties and surface hydrophobicity (using MATLAB software) was compared with the service life of a new compound subjected to accelerated aging tests. Prediction of service life is helpful for replacement of aged insulators from service to avoid interruption in power transmission.
RESUMEN
A series of novel ionic cross-linked chitosan (CS) based hybrid nanocomposites were prepared by using polyaniline/nano silica (PAni/SiO2) as inorganic filler and sulfuric acid as an ionic cross-linking agent. The CS-PAni/SiO2 nanocomposites show enhanced mechanical properties and improved oxidative stabilities. These nanocomposites can be effectively used as environmental friendly proton exchange membranes. Incorporation of PAni/SiO2 into CS matrix enhances water uptake and facilitates the phase separation which enables the formation of hydrophilic domains and improves the proton transport. Moreover, the doped polyaniline also provides some additional pathways for proton conduction. The membrane containing 3wt% loading of PAni/SiO2 in chitosan (CS-PAni/SiO2-3) exhibits high proton conductivity at 80°C (8.39×10-3Scm-1) in fully hydrated state due to its excellent water retention properties. Moreover, methanol permeability of the ionic cross-linked CS-PAni/SiO2 nanocomposite membranes significantly reduces with the addition of PAni/SiO2 nano particles. The CS-PAni/SiO2-3 composite membrane displays the best overall performance as a polymer electrolyte membrane.
RESUMEN
Polymeric outdoor insulators derived from polydimethyl siloxane (PDMS) are replacing conventional ceramic insulators in high voltage power transmission lines because of their improved electrical, mechanical and hydrophobic performance. Major impediments like failure of polymeric insulators due to natural aging by UV radiation from sunlight and electrical tracking have limited their usage. Herein, it is demonstrated about the usage of manganese dioxide based nanoparticles as an effective agent to prevent the UV accelerated aging of polymeric insulators. MnO2 nanoparticles of different shapes and dimension were synthesized using a single step wet chemical reaction between KMnO4 and methyl acetate. Namely, 2D δ-MnO2 nanosheets, 1D α-MnO2 nanowires and 3D α-MnO2 nanorods were formed. These nanoparticles were extensively characterized by various techniques. In the scope of the study, the δ-MnO2 (10-5 S cm-1; 1 MHz) nanosheet demonstrated the lowest electrical AC conductivity and a higher band gap compared to the 1D (10-4 S cm-1; 1 MHz) and 3D variety (10-4 S cm-1; 1 MHz). Owing to the lower electrical conductivity of the δ-MnO2 nanosheet, it was further incorporated at different filler volumes in the polymeric matrix (blend of polydimethyl siloxane/ethylene vinyl acetate) as a UV protector material for the polymer based high voltage composite polymeric insulator. The UV protection ability, induced by the δ-MnO2 nanosheet, was achieved without adversely affecting other properties of the formulated insulator compound material. The optimum properties of the composite were found to be obtained at 3 phr (three parts of δ-MnO2 nanosheet per hundred parts of polymer) loading of the nanosheet. The current work will promise to pave a new pathway for the generation of UV resistant high voltage power transmission line insulator materials. It would be interesting in the future to study the effect of incorporation of manganese dioxide based nanosheets on the UV resistant properties of different polymeric matrices.
RESUMEN
The fabrication of scalable and affordable conductive Ketjen carbon black (K-CB)-elastomer composites for adjustable electromagnetic interference (EMI) shielding remains a difficult challenge. Herein, chlorinated polyethylene (CPE)-K-CB composites have been developed by single step solution mixing to achieve high EMI shielding performance associated with absorption dominance potency by conductive dissipation as well as the reflection of electromagnetic waves. The dispersion of K-CB inside the CPE matrix has been corroborated by electron micrographs and atomic force microscopy (AFM). The K-CB filler and CPE polymer interaction has been investigated through the bound rubber content (Bdr) and the dynamic mechanical properties. The relatively low loading of K-CB with respect to other conventional carbon fillers contributes to a promising low percolation threshold (9.6 wt% K-CB) and a reasonably high EMI shielding effectiveness (EMI SE) value of 38.4 dB (at 30 wt% loading) in the X-band region (8.2 to 12.4 GHz). Classical percolation theory reveals that the electrical conduction behavior through the composite system is quasi-two dimensional in nature. Our belief lies in the promotion of scalable production of flexible and cost-effective K-CB-CPE composites of superior EMI SE to avoid electromagnetic radiation pollution.
