Experimental investigation on hydrophobic behavior of carbon spheres coated surface made from microplastics

In this paper, a simple method to plate a hydrophobic coating on the inner surface of a small-scaled tube was proposed, where the coating consisted of carbon microspheres. Three common plastics polystyrene, polycarbonate and polyethylene were used as the feedstocks to be processed in supercritical water in a quartz tubular reactor. After reaction, the contact angle of droplet on the inner surface of the quartz tube was turned out to be over 100°, significantly larger than that of the blank tube 54°. When processing polystyrene in the 750^°C supercritical water for 10 min, the largest contact angle was obtained, up to 145°. Besides, in this sample, the size of carbon spheres was smallest, about 2.09 μm diameter on average. When comparing among different types of plastics under the same condition, the contact angle of surface made from PC took the dominant position over that of PS and PE, 124°, 100° and 90°, respectively. In the sample made from PC, carbon spheres adhered into a mountainlike shape, producing a binary geometric structure. Furthermore, this research could be helpful in the discussion of plastic waste management and carbon spheres fabrication with low cost.