Waterproof Coating Set to Reduce Reliance on Plastic

Water-Repellent Coating Could Reduce Reliance on Plastic Research into reducing plastic use across numerous and varied applications is extensive. With this in mind, researchers have found a way to impart some of plastic's useful properties to relatively sustainable paper materials in a simple, cost-effective and efficient manner. A coating called Choetsu not only makes paper water-repellent, but also preserves its flexibility and enables it to degrade safely. The study addressing this coating was published in Industrial & Engineering Chemistry Research. Plastic materials are generally harmful to the environment. Plastic pollution that washes onto beaches, devastates rivers and kills countless animals is well known to everyone. Nevertheless, overcoming this problem appears quite difficult given that plastic materials are found nearly everywhere in daily life. Professor Zenji Hiroi from the Solid State Physics Institute at Tokyo University and his team are investigating ways that materials science can help. The team's latest discovery aims to replace some plastic uses with a more sustainable material like paper. Hiroi said, "From what I see, the fundamental problem with plastic materials is that they cannot degrade quickly and safely. There are materials like paper that can degrade safely, but of course paper cannot fulfill many of the diverse uses of plastic. However, we have found a way to give paper some of plastic's good properties, and in a harmless manner. We call this Choetsu; a low-cost, biodegradable coating that adds water-repellency and strength to simple paper. Without harmful effects." Choetsu is a combination of materials that, when applied to paper, automatically forms a strong and water-repellent film upon contact with moisture in the air. The coating consists mostly of methyltrimethoxysilane, some isopropyl alcohol and a small amount of tetraisopropyl titanate—safe and low-cost chemicals. Paper structures, such as food containers, are sprayed or dipped into this liquid mixture and dried at room temperature. Once dry, a thin silica layer containing methyl, a type of alcohol, forms on the cellulose that makes up the paper, providing strong and water-repellent properties. Additionally, reactions occurring during the coating procedure automatically create a layer of titanium dioxide nanoparticles. These exhibit photocatalytic activity, a property that repels dirt and bacteria, protecting the coated product for an extended period. All chemicals involved in the coating eventually transform into harmless substances such as carbon, water and silicon-like sand. Hiroi said, "We have overcome the technical challenges and use of this coating in products used for food consumption, packaging or storage could soon be realized. We now hope to apply this approach to other types of materials. The liquid composition can be adjusted for other materials and we can increase their utility by creating a dirt and mold-resistant coating that can form on glass, ceramics and even other plastics. Along with researcher Yoko Iwamiya and the rest of my team, who have been working in this field for some time, I hope we can do something truly beneficial for the world." Academic Reference: Yoko Iwamiya et al, Photocatalytic Silica–Resin Coating for Environmental Protection of Paper as a Plastic Substitute, Industrial & Engineering Chemistry Research (2022). DOI: 10.1021/acs.iecr.2c00784 Source