What are the fully degradable materials of plastics?

The ubiquitous plastic products facilitate people's life, but the resulting plastic waste causes a lot of pollution to the ecological environment. The white pollution caused by plastic products led by plastic bags is gradually harming the natural environment and people's normal life. Plastic is a kind of synthetic polymer chemical products, most of the plastic is non-renewable petroleum as raw material, by polyol and polyacid condensation. Unlike other types of waste, decomposer microbes in the environment can't digest the chemical bonds that hold the monomers together in degradable plastic, so they can't break it back down into its monomer form. In other words, once plastic is synthesized, there is no going back.

In addition to environmental awareness and reducing the use of single-use plastics, another important way to deal with "white pollution" is to replace ordinary plastics with biodegradable ones. By optimizing the selection of raw materials and production process, biodegradable plastics can gradually decompose into fragments under the combined action of several days or months of sun, rain and microorganisms, and finally completely degrade.

Biodegradable materials can be generally divided into photodegradable plastics, biological degradable plastics, photodegradable/biological degradable plastics and water degradable plastics and other four categories. Photodegradable plastic is mixed with a photosensitizer in plastic, under the action of sunlight, plastic gradually decompose. However, the disadvantage is that the degradation time is affected by sunlight and climatic conditions, so it cannot be controlled. Biodegradable plastics are plastics that can be broken down into low molecular compounds by microorganisms that exist in nature, such as bacteria, molds and algae, under certain conditions. This kind of plastic is convenient to store and transport and has a wide range of applications. Photobiodegradable plastics are plastics that combine the dual characteristics of photodegradable plastics and biodegradable plastics. Water-degradable plastics are plastics that dissolve in water due to the addition of water-absorbing substances. With the development of modern biotechnology, biodegradable plastics have become a new hotspot in research and development.

At present, China's research and development of biodegradable plastics are mainly biological polyester such as polylactic acid (PLA), poly hydroxyfatty acid ester (PHA), carbon dioxide copolymer (PPC), etc.. Polylactic acid (PLA) is formed by the polymerization of lactide monomer extracted from plant sugars, which can be completely degraded into water and carbon dioxide under industrial compost. Polyhydroxyfatty acid ester (PHA) is aliphatic copolymer with different structure synthesized by microorganisms through fermentation of various carbon sources, which can not only be used in packaging materials, agricultural film, etc., but also widely used in medicine, cosmetics, animal feed and other fields.