Plastic waste accumulates in the heart of the oceans and on the ground and tiny plastic particles enter our bloodstream. As long as there are no suitable substitutes for the common industrial material, this pollution is expected to continue and even increase. Weizmann Institute of Science scientists present a possible candidate for the task: strong, cheap and biodegradable plastic
Our world is loaded with billions of tons of plastic, most of which is stored in the soil and in the heart of the oceans or crumbles into particles (microplastics) that float in the air and accumulate in the water, and thus penetrate the plants and our blood circulation and that of other animals. The danger of plastic is increasing year by year, because it is made of huge molecules called polymers which do not break down quickly. Today there is a limited selection of biodegradable plastic materials, which make up less than a fifth of the amount of plastic produced and their decomposition processes are relatively cumbersome.
Research by Dr. Angelica Niyazov-Elkan, Dr. Haim Wiseman and Prof. Boris Rybchinsky From the Department of Molecular Chemistry and Materials Science at the Weizmann Institute of Science, ShPublished in the scientific journal ACS Nano, found a new composite material that is easy to decompose by bacteria, created by connecting a biodegradable polymer with crystals from a biological material and enjoys an effective combination of simplicity of preparation, low price and great strength. The late Dr. Eyal Shimoni, Dr. Xiaomeng Sui, Dr. Yishai Feldman and Prof. Daniel Wagner also participated in the study.
In the current era, the various industries are enthusiastically adopting composite plastic materials, which are created by mixing two or more pure materials, and allow to enjoy the combination of their properties, such as, for example, blending lightness with flexibility and strength. The high functionality has made the composite plastic a central component in a wide variety of industrial production processes, from airplanes and cars to bicycles. In order to examine whether it is possible to create a composite plastic material that may meet industrial needs while maintaining environmental friendliness, the researchers decided to choose common and cheap materials whose properties can be improved. They recognized that molecules of tyrosine, one of the common amino acids, whose crystals are particularly strong, could be an effective component in a biodegradable composite plastic. After examining the combination of tyrosine with several polymers, they chose the material ethyl cellulose, a common derivative of cellulose (cellulose), which is widely used in the production of medicines and care products.
Ethyl cellulose alone is a weak material that crumbles easily. To combine it with tyrosine, it was dissolved together with it in boiling water. After cooling and drying, an extremely strong composite plastic is formed, made of fiber-like tyrosine crystals that have grown into and integrated into the ethyl cellulose. Evidence of the strength of the newly created composite material became clear when a sheet of the biodegradable plastic with a thickness of 40 microns withstood the lifting of a 6 kg weight. Along with this, it was discovered that the material has other unique properties that increase its usefulness. Usually, when a material is strengthened, it loses its plasticity. However, along with the great strength of the new composite material, it turned out that it stretches more than its main raw material - ethyl cellulose. The combination of the materials created a synergistic effect, which is reflected in the appearance of extraordinary properties, and therefore have great potential for industrial needs. In addition, since both cellulose and tyrosine, whose crystals are found in several types of hard cheeses, are edible substances, the composite and biodegradable plastic material can even be edible. Is it also tasty? Meanwhile, since the production environment in the lab is not food safe, the scientists have not experimented with it themselves.
Prof. Rivchinsky concludes: "Continuing research that we have started may advance the commercial potential of the new material, since we replaced the dissolution in water with melting, as is customary in industrial plants; that is, heating the biodegradable polymers until they become liquid, then mixing them with the tyrosine or other suitable substances. If we succeed in solving the scientific and technical challenges involved in this process, it will be possible to test production of the composite plastic at scale extensive".
