Classic folding paper crane made of paper coated with Choetsu (left) and uncoated (right). When submerged in water, the coated paper cranes retain their shape, while the uncoated ones quickly become saturated with water and begin to disintegrate. Photo by Quan Hirai 2nd Class To

Intern Reporter for Science and Technology Daily   Zhang Jiaxin

In the future, people may be able to pack milk tea in A4 paper with the help of coating. According to a study published on the 13th in the journal of Industrial and Engineering Chemistry Research, published by the American Chemical Society, researchers at the University of Tokyo in Japan have for the first time found a simple, economical and efficient way to "endow" some of the characteristics of plastic into relatively sustainable paper materials: A coating called Choetsu can not only make the paper waterproof, but also keep it flexible and biodegradable.

"In my opinion, the main problem with plastic materials is that they don't degrade quickly and safely." Koji Hirai, a professor at the University of Tokyo's Institute of solid-state Physics, said that while materials like paper can be safely degraded, they do not meet the wide range of uses of plastic materials. Now, new methods can give paper some of the good properties of plastic, but without any adverse impact on the environment.

Choetsu is a combination of materials that, when applied to paper, spontaneously creates a strong waterproof film when it comes into contact with moisture in the air. The coating is made up of safe and low-cost chemicals, primarily methyl trimethoxy-silane, some isopropyl alcohol and a small amount of tetraisopropyl titanate. Structures made from paper, such as food containers, are sprayed or dipped into this coating and dried at room temperature, and once dry, a thin layer of silicon dioxide containing methyl groups forms on the cellulose that makes up the paper, providing strong water resistance.

In addition, the reactions that occur during the coating process automatically create a layer of titanium dioxide nanoparticles that produce dirt and bacteria-repellant properties that protect the coated item for an extended period of time. Over time, all the chemicals involved in the coating break down into harmless substances such as carbon, water, and sandy silicon.

Hiroi said that in the future, he hopes to use this method for other types of materials as well. At the same time, the liquid composition could be tweaked for other materials to create a stain and mildew resistant coating that could be applied to glass, ceramics and even other plastics.

Plastic Industry Video