A green alternative to plastic → breathable and waterproof paper "armor"!

Imagine if you could put a soft and waterproof "armor" on paper, making it waterproof like plastic, but also degradable like paper. How great would that be?

Now, that dream has become a reality. Japanese scientists have developed this innovative technology that can transform ordinary paper into a green alternative to plastic. What's even more incredible is that this paper airplane can withstand Mach 7 wind tunnel tests!

[Note: The original image comes from this paper. The upper image (a) shows a coated paper airplane in a wind tunnel. The lower image shows the shock wave generated by Mach 7 wind.]

This technology is like putting a special "breathable raincoat" on paper fibers. Scientists use a compound called silane to form a porous coating only a few microns thick on the surface of paper fibers. This coating is like composed of countless tiny "honeycombs", making the paper both waterproof and flexible. By immersing paper or paper products in a low-viscosity liquid mainly composed of alkoxysilanes and then drying them under ambient conditions, a porous silica resin layer several microns thick will be uniformly formed on the cellulose fibers. The porous silica resin layer provides excellent durability and waterproofness for the paper while retaining the original texture and flexibility of the paper. The resulting organic-inorganic composite material can replace many plastic products and is easily decomposed in the natural environment without causing pollution.

[This figure is a schematic diagram of the use of super coatings in the paper to form a silica film on the cellulose fibers that make up the paper. First, the methyltrimethoxytetrahydrogenated silicon molecules in the coating solution (upper left of the figure) will undergo a hydrolysis reaction with the water molecules present in the paper and the air to generate Si-OH tetrahydrogenated silicon alcohol groups. Then, the tetrahydrogenated silicon alcohol groups of two methyltrimethoxytetrahydrogenated silicon molecules are connected by a dehydration reaction to form a siloxane bond. Finally, the tetrahydrogenated silicon alcohol groups of the methyltrimethoxytetrahydrogenated silicon molecules undergo a dehydration reaction with the hydroxyl groups on the cellulose fibers and are fixed to the surface of the fibers via Si-O-C bonds (lower right of the figure). There are a large number of voids in the resulting siloxane network, so the paper is very soft, and the methyl groups (R) remaining in the voids are water-repellent. ]

This process is very cleverly designed, just like weaving a sophisticated net on paper fibers. First, scientists use a special "primer" (tetraisopropyl titanate) to start the reaction, just like the first stitch in weaving. Then, the silane molecules will automatically "hold hands" to form a protective net on the surface of the paper fibers. This net not only tightly "holds" the paper fibers, but also maintains a porous structure like breathing. This silica-coated paper is harmless to the human body because the additives do not contain organic fluorine compounds, boron compounds or alkyltrialkoxysilanes. The treated paper exhibits amazing properties:

Ⅰ. It can be soaked in water for 72 hours without deformation

Ⅱ. Maintain the original flexibility and can be folded at will

III. The strength is greatly improved, and even paper airplanes that can withstand the impact of high-speed airflow can be made

IV. Most importantly, it can be safely degraded in the natural environment

【Note: Figure (b) shows the block formed after the coating solution solidifies. Figure (c) shows a drop of water dripping onto coated paper. Figure (e) shows a paper product coated with a super coating. Figure (d) shows a photo of coated (left) and uncoated (right) paper straws after being soaked in water for 3 days. 】

The significance of this technology goes far beyond this. In our world, millions of tons of plastic waste enter the ocean and soil every year, forming microplastics that are difficult to degrade, threatening marine and terrestrial ecosystems. This improved paper can not only replace a large number of disposable plastic products in daily life, but also return to nature safely after use, without leaving a permanent environmental burden.

This is like a cycle: fiber is obtained from trees and plants to make paper, the paper's performance is enhanced in an environmentally friendly way, and it returns to nature after use. This technology demonstrates the power of scientific innovation and also reflects the wisdom of people's pursuit of harmonious coexistence with nature.

This innovation has far-reaching implications for the future. It tells us that environmental problems can be solved by more than just restrictions and prohibitions. Through technological innovation, we can find solutions that meet people's needs while being friendly to the environment. This is also the true meaning of sustainable development: meeting the needs of the present without affecting the ability of the next generation to meet their needs.

As this study demonstrates, human creativity is limitless. Through constant innovation, we can find ways to live in harmony with nature and preserve a blue planet for the future.

Image citation and paper source:

Modern Alchemy: Making “Plastics” from Paper. Yoko Iwamiya, Masayoshi Kawai, Daisuke Nishio-Hamane, Mitsuhiro Shibayama, and Zenji Hiroi. Industrial & Engineering Chemistry Research 2021 60 (1), 355-360. DOI: 10.1021/acs.iecr.0c05173