[Chemical Knowledge]：How does plastic degrade?

In today's society, plastic products have become an indispensable daily necessities in life, but it also brings serious pollution problems. Because the decomposition cycle of plastics is very long and there are many types, it is almost an unsolvable problem to deal. The accumulation of plastic waste has caused a serious threat to the environment and ecological health. Therefore, how to decompose plastics efficiently has become an important issue.

1. The principle of plastic degradation

plastics are high molecular compounds composed of polymers, which are divided into two categories: ordinary plastics and biodegradable plastics. Ordinary plastics are synthesized from chemical raw materials such as petroleum and cannot be quickly decomposed, while biodegradable plastics are made of natural raw materials such as starch and can be biodegraded into organic matter. There are three main principles for the degradation of

plastics, namely, biological degradation, chemical degradation and photodegradation.

biodegradation: the use of sunlight, microorganisms, food chain and other factors, so that the plastic molecules react, and finally it is decomposed into natural organic matter. Among them, microorganisms are the biggest regulating factors for degrading plastics. In the natural environment, many microorganisms can catalyze the decomposition of plastics, so that the degradation of plastics becomes faster.

chemical degradation: the plastic is placed in a chemical solution (such as an oxidizing agent) for treatment. The principle of chemical degradation is to oxidize the plastic, so that the chemical bond is broken, and finally the plastic is decomposed.

photodegradation: exposure of plastic to the sun. The principle of photodegradation is that the chemical bonds in the plastic will be destroyed by the sun's energy, thus causing the plastic to decompose. And different colors and different materials of plastic degradation rate is also different.

2. Plastic degradation methods

biodegradation, chemical degradation and photodegradation are three common plastic degradation methods, which will be described in detail below.

biodegradation

biodegradation is one of the most widely studied and economical methods. Biodegradation products are widely available, cheap and easy to degrade. For example, vegetables, fruits, etc., these substances contain enzymes and other compounds that degrade plastics, which can decompose plastics into small molecules and process them into organic fertilizers through microbial degradation. In contrast, biodegradation has an obvious disadvantage, the biodegradation process is not stable enough, will be affected by environmental factors, and the degradation process is not fast enough.

chemical degradation

chemical degradation is a common and effective method, and it is an important technology developed after the 1950 s. However, this method will produce a certain degree of pollution, the use of chemicals to complete the degradation process of plastics. Chemical degradation is divided into thermal cracking and oxidative degradation, thermal cracking is the decomposition of plastics by heating, oxidative degradation is the use of oxidants to dissolve plastic molecules. Chemical degradation methods are energy and cost intensive.

photodegradation

photodegradation is the use of sunlight or ultraviolet light to decompose plastics. Sunlight is the core of photodegradation, and different types of plastics use sunlight differently. This method will not cause great harm to the environment, only need a close to the natural state of the processing place, different colors of plastic degradation rate is different.

3. Conclusion

At present, biodegradation and photodegradation are proven methods, especially photodegradation is gradually being widely used. China's research and application obviously lags behind the developed countries, and it is necessary to increase efforts in scientific research, policy guidance and market leadership, promote biodegradation and photodegradation processes, and comprehensively improve the degradation capacity and environmental protection performance of plastics. As consumers, we can also pay more attention to conservation and recycling, and plastic waste that cannot be degraded should be collected, recycled and disposed.

in the context of building a beautiful China, the treatment of plastic waste is not only a major environmental governance task, but also a severe test, which will be a long-term project of environmental protection. By scientifically degrading plastic waste, the whole society will benefit and leave a better environment for future generations.