The Chinese Academy of Sciences successfully developed seawater degradable plastics, hoping to take the lead in the application and promotion of plastic bottle manufacturers

Seawater degradable plastic products, the appearance is no different from ordinary plastic.

Comparison of the degradable plastic samples of seawater (upper) and well-preserved samples (lower) after soaking in seawater for 3 months. (This photo is provided by the interviewee in addition to the data map)

On June 13, the Department of Science and Technology of Hainan Province and the Institute of Physics and Chemistry Technology of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Physics and Chemistry of the Chinese Academy of Sciences) signed a strategic cooperation agreement in Haikou. The two parties will jointly build the Hainan Provincial Degradable Plastics Technology Innovation Center to study new technologies in the field of degradable plastics , New products, new processes, etc., promote the pilot test of seawater degradable plastic technology in Hainan (that is, the test before the product is officially put into production), and realize the industrialization of seawater degradable plastic as soon as possible, which is a comprehensive “plastic ban” work for Hainan. Inject the power of science and technology.

Seawater biodegradable plastics are at the heart of this cooperation. What is seawater degradable plastic? Why develop it? With these questions, a reporter from Hainan Daily interviewed Ji Junhui, a researcher at the Institute of Physics and Chemistry of the Chinese Academy of Sciences and director of the National Engineering Research Center for Engineering Plastics.

"Seawater-degradable plastics are polyester composite materials that can degrade in seawater." Ji Junhui said that it was developed to solve the increasingly serious problem of marine plastic pollution, replace difficult-to-degrade general-purpose plastics, and protect the marine ecological environment. The work of'plastic ban' has been started, and Shanghai South is a major marine province. The sooner seawater degradable plastics are applied, the better, and the wider the scope, the better."

Marine plastic waste pollution is beyond imagination

At present, plastic pollution has become another major threat to climate change on the planet, because it is rapidly polluting every natural system and endangering more and more organisms.

"Since the 1960s, people have begun to pay attention to the problem of plastic pollution. Since humans have a deeper sense of plastic pollution on land, scientists are the first to find a solution to the problem of plastic pollution on land." Ji Junhui said, this is only us Now commonly used biodegradable plastics.

But in fact, marine plastic waste pollution and their harm to the marine ecological environment have already far exceeded our imagination. "Currently, the earth produces more than 300 million tons of plastics each year, and a large part of them are directly thrown into the ocean after use, and some of them eventually enter the ocean through rivers and wind from the land." Ji Junhui said that the current human activities and ocean currents have caused these plastic wastes to concentrate Distributed in the North Pacific, South Pacific, North Atlantic, South Atlantic and Central Indian Ocean.

"The use of plastics has increased in recent years. It is estimated that if there is no significant change in the current consumption of plastics, by 2050, the total weight of plastics in the global ocean will exceed the total weight of fish." Ji Junhui said, this It is a very terrible thing. At present, there is a "plastic island" between Hawaii and California in the United States. 1.6 million square kilometers are all plastic. Many people jokingly call it "the eighth continent of the world."

"We must know that almost all types of plastics have been found in the ocean." Ji Junhui said that they are continuously affected by light, weathering, vortex machinery and biota in seawater, and eventually form "microplastics" with a diameter of less than 5 mm. These plastic particles either float in the sea water or sink to the bottom of the sea, and will not decompose for decades or even hundreds of years, causing serious pollution to the entire marine environment.

The dispersed plastic particles in the ocean have devastated countless seabirds, fish and other marine life, and gradually brought toxins to humans through the food chain. "Chinese scientists have found that the average edible salt contains a ‘microplastic’. This is the consequence of non-degradable plastic entering the ocean. This is not alarmist, it’s a marine pollution problem that humans must face directly,” said Ji Junhui.

Unlike the treatment of "white pollution" on land, people can hardly collect and process fine plastic particles extensively. "The control of marine plastic pollution is becoming more and more urgent, and it is also difficult." Ji Junhui said that the most fundamental and effective way to solve this problem is to let the plastic degrade and disappear after entering the seawater, so the development and use can degrade itself in the marine environment. Plastic products, replacing refractory plastic products, is imminent.

Biodegradable plastics cannot be degraded in seawater

In order to curb the spread of "white pollution", plastic bottle manufacturers have unanimously launched the "plastic restriction" or even "plastic restriction" work. At present, more than 60 countries and regions around the world have issued relevant policies or laws restricting the use of plastic bottle manufacturers' plastics. With the deepening of scientific research, polylactic acid (PLA), polybutylene succinate (PBS) and its copolyester (PBAT), polycaprolactone (PCL) and polyhydroxyalkanoate (PHAs), etc. Biodegradable materials (biodegradable plastics) have largely replaced non-degradable general-purpose plastics, which has alleviated "white pollution" on land to some extent.

So, can seawater degrade biodegradable plastics? The answer is no.

Most of the biodegradable plastics are polymer materials containing ester bonds. The molecular chains are relatively fragile and can be decomposed and digested by many microorganisms in nature, and eventually form carbon dioxide and water. "Unlike terrestrial soil, the microbial biomass in seawater is very small, and the temperature of seawater is relatively low. Biodegradable plastics cannot be degraded in seawater like they are on land, or they cannot be degraded by seawater for a long time." Ji Junhui said Therefore, researchers need to develop new polymer materials that can degrade in the marine environment.

The current international research on seawater degradable materials has just started. "Although seawater degradable plastics have been highly valued by global experts, the international research on seawater degradable plastics is still rare. Only a few multinational companies and scientific research institutions in China, Japan, Germany and other countries have begun to study." Ji Junhui said, 2017 In 2010, the National Engineering Research Center for Engineering Plastics and the Institute of Physics and Chemistry of the Chinese Academy of Sciences organized nearly 10 PhDs to study seawater degradable plastics, leading the country.

Starting from the molecular structure design, after difficult research and repeated experiments, in 2018, Ji Junhui team developed a polymer material that can be degraded in seawater, which can be understood as the "predecessor" of seawater degradable plastic products.

"This new material is not only degradable in ocean water, but also degradable in soil. It can be decomposed into substances such as water and carbon dioxide in days or hundreds of days when it is discarded into the soil or the ocean." Ji Junhui It said that although seawater degradable plastic was born, it is still at the laboratory level, and it has a long way to go before it is put into production.

Is expected to reduce the increase in human plastic pollution

Generally speaking, plastics entering the ocean are roughly divided into two categories, one is plastic waste and the other is plastic products used in the ocean. "According to the different uses of plastic products, we have to choose different performance seawater degradable polymer materials." Ji Junhui said.

For example, fishing nets are common plastic products. In order to prevent marine plastic waste, future fishing nets need to be made of seawater degradable plastics. "Fishing nets are used for fishing. They cannot be degraded as soon as they are put into the sea. Otherwise, the cost of fishing is too high." Ji Junhui said, so researchers must consider the service life of fishing nets in seawater and prolong their degradation time. "It takes longer to degrade" is one of the properties of this polymer material. .

In this way, if plastic products such as discarded packaging boxes, plastic wraps, and fibers enter the ocean, then they are plastic waste. "Then we need to shorten the time of degradation." Ji Junhui said that these different needs in production and life It is also a factor that researchers need to consider in R&D.

Since 2018, with the assistance of the Institute of Deep Sea Research, Chinese Academy of Sciences and Sansha plastic bottle manufacturers, Ji Junhui’s team has conducted degradation tests and screening of seawater degradable polymer materials in different marine environments such as the Bohai Sea, East China Sea and South China Sea, and has finalized different applications. In the future, they can design materials with different properties according to different applications.

"The sea trial was conducted to study the time that different polymer materials do not significantly reduce performance in different marine environments (that is, the possible service life of the product in the future), and the rate of degradation and disappearance, so as to judge the performance of plastics for development and application." Ji Junhui said that the current sea trial of seawater degradable plastics has achieved preliminary results in the preparation of seawater degradable plastics, and the next step is to solve engineering and technical problems and prepare for industrial demonstration.

"Degradable plastics in seawater can not only degrade in seawater, but also in terrestrial soil." Ji Junhui said that the treatment of marine pollution is to fight for the survival of human beings. All the efforts they have made are for human consumption of plastics. Under the premise of continuous increase, do our best to reduce the increase of plastic pollution.

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