Spray a spray, the paper becomes “plastic” for a wide range of purposes

When immersed in water, the Choetsu-coated paper crane (left) retains its original shape, while the ordinary paper crane (right) is quickly soaked in water and begins to decompose. Image credit: Zenji Hiroi

We may have seen plastic objects wash up on beaches, destroy rivers and even kill countless animals. At present, for the sake of human self-interest and the protection of the environment, there is considerable research on the reduction of plastics and their applications.

Researchers at the University of Tokyo in Japan have found a simple, cost-effective and efficient way to make relatively sustainable paper materials have some of the useful properties of plastics for the first time. A coating called Choetsu not only makes the paper waterproof, but also maintains its elasticity and is biodegradable. The paper was recently published in the American Chemical Society’s Industrial and Engineering Chemistry Research.

Plastic materials are often harmful to the environment, which is a fact that is difficult to escape. However, given the ubiquity of plastic materials in everyday life, the problem seems beyond people’s control. The university of Tokyo institute of solid state physics professor Zenji Hiroi and his team’s research aims to replace some uses of plastic with more sustainable materials: paper.

Hiroi said: “In my opinion, the main problem with plastic materials is that they cannot degrade quickly and safely. There are some materials that can be safely degraded, such as paper, but it is clear that paper cannot meet the wide range of uses of plastics. Our new method gives paper some of the finest properties of plastic without causing any damage. ”

Choetsu is a composite material that, when applied to paper, automatically generates a strong waterproof film when it comes into contact with moisture in the air. The coating consists of safe and low-cost chemicals, mainly methyl trimethoxysilane, some isopropanol and a small amount of tetraisopropyl titanate.

For example, food containers made of paper are sprayed or immersed in this liquid mixture and dried at room temperature. After drying, a thin layer of silica containing methyl (an alcohol) is formed on the cellulose that makes up the paper, thus providing strong water resistance.

In addition, the reaction that occurs during the coating process automatically generates a layer of titanium dioxide nanoparticles. This creates a dirt repellent property called photocatalytic activity that protects the coating over a longer period of time. All of the chemicals involved break down into harmless substances such as carbon, water, and sandy silicon over time.

“The technical challenges are complete, and some applications may soon be realized, such as items used to consume, package or store food.” “At the same time, the chemical composition of the liquid can be adjusted for different materials, creating a coating that is anti-fouling and anti-mold, and applied to materials such as glass and ceramics to expand its use,” Hiroi said. (Source: China Science Daily Wang Fang)

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