| Abstract: |
The low melting point and soft nature of polyethylene have posed difficulties in the metallization process using thermal spray techniques at high temperatures. In this research, the first ever study on spraying metallic coatings on a porous polymer using a twin wire-arc spray process is reported. Commercially available porous polyethylene sheets, 3 mm in thickness, with average pore size of 70 µm were used as substrates. Copper, aluminum, and zinc were successfully deposited on the polymer, with no prior surface preparation, to form coatings with thickness of up to 400 µm. The adhesion strength on the coatings was found to be greater than the yield stress of the polymer; so, the substrate fractured before the coating detached. The elemental composition of the coatings was determined by energy dispersive X-ray spectroscopy. Coating surface morphology and cross-sections were examined using a scanning electron microscope. Metal particles, which had a mean diameter of 30-40 µm, were observed to penetrate deep into the surface pores. The resulting mechanical interlocking of the metal with the polymer resulted in high adhesion strength. Tests were done in which the spray was passed through an orifice 1 mm in width before impacting on the substrate so that after a single pass of the spray torch over the polymer surface individual metal splats could be observed. Splats were observed to adhere to pores and crevices in the polymer surface. These results suggest that the porosity in the polymer helps not only in overcoming the challenges in metallizing polyethylene, but also provides a significant reduction in the weight of the polymer. Therefore, all these properties helped in fabricating an extremely lightweight composite material with potential applications in electronic cooling.
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