Preparation and Characterization of Polyurethane/Carbon/Organoclay Composite for Coating of Aluminum Conductor Overhead Lines

Abstract

Electrical transmission overhead lines use an aluminum conductor in services. However, protection of the aluminum conductor from corrosion has to be considered. Hence, an extensive experimental work was done to prepare the composite coating of the aluminum conductor. Three types of polyurethane composites were fabricated with different fillers (5 wt% carbon and 5 wt% organoclay) and were characterized. The composites were polyurethane/carbon (PC), polyurethane/organoclay (PClay), and polyurethane/carbon/organoclay (PCClay). Thermogravimetry analysis and Fourier transform infrared spectroscopy were conducted to obtain thermal properties and chemical bonding of the composites. To obtain the corrosion resistance, salt spray tests were applied. To obtain hydrophobicity properties, the contact angle between water and the composites was measured. Measurements of composites relative permittivity was conducted to obtain dielectric properties. A water vapor permeability test was conducted to obtain the rate of water/gas vapor discharge. Finally, an adhesion test was conducted to obtain adhesion performance according to the ASTM D3359 standard. Based on characterization, PCClay had better characters to be used as an overhead aluminum coating material followed by PC and PClay.

Effect of Carbon and Organoclay Fillers on Partial Discharge and Corrosion Properties of Polyurethane Base Composite Coated on Aluminum Alloy

“…The results of the potentiodynamic polarization test shows that the corrosion rate of the aluminum alloy coated with PCClay is lower than that of the aluminum alloy without the coating. Even when the surface of the aluminum alloy is covered with the composite, the water vapor or other substances in a very small portion can permeate the composite to reach the surface of the aluminum alloy [12]. The vapor acts as an electrolyte, which electrically connects the aluminum surface to the surface of the composite or to the outer part of the samples.…”

“…The corrosion process depends on the electrical resistance of the materials that cover the surface of the aluminum alloy. Polyurethane is a dielectric, but the vapor penetrates in a limited portion [12]. This vapor can act as a conductor to transport electrons from the surface of the coating to the surface of the aluminum alloy.…”

“…Generally, E corr of materials shifts to more cathodic if the surface is not easily oxidized. It seems that the PCClay3 composite covers the surface of the aluminum alloy with good adhesion between the composite and the aluminum alloy [12]. On the other hand, as the filler content increases from 3 to 5 wt%, agglomeration and imperfection are more likely to occur.…”

“…The addition of carbon graphite improves the fire resistance of polyurethane foams but deteriorates the bending strength due to poor adhesion to the polyurethane matrix [11]. The polyurethane/carbon/organoclay composites have been studied as a coating that contributes to reducing corrosion [12]. Extensive studies have also been conducted on partial discharge, particularly on the insulator material.…”

“…In the case of an epoxy resin insulator, it has been confirmed that the discharge resistance could be improved by adding a small amount of nano-inorganic filler [13−15]. A previous study reported that the thermal stability, dielec-tric, adhesion to the aluminum alloy, and water vapor permeability properties were affected by the carbon and organoclay as a filler [12].…”