Degradable plastics technology research and development

The plastics industry has developed rapidly. At present, the total output of plastics in the world has exceeded 170 million tons. Its uses have penetrated into all sectors of the national economy and people's lives, and have become the four pillar materials along with steel, wood, and cement. However, plastics have the disadvantage that they are difficult to degrade in the natural environment or in the garbage yard after use, and thus become wastes that pollute the environment. According to statistics, the mass fraction of plastics in municipal solid waste has reached more than 10%, and the volume fraction is about 30%. The development of biodegradable plastics can reduce white pollution and have significant economic and social benefits.

At present, research and development of degradable plastics are very active, and some have entered industrial production. In general, the current degradable plastics still need to further study the technology, improve performance, reduce costs, broaden the use and gradually introduce it to the market.

At present, the countries that produce degradable plastics mainly include the United States, Italy, Germany, Canada, Japan, and China. The United States is one of the major countries in the development of degradable plastics. There are more than a dozen units, such as the Plastic Degradation Research Complex (PDRC) and the Biological/Environmental Degradable Plastics Research Association (BEOPS), whose purpose is to conduct the synthesis and processing of degradable plastics. Establishment of process, degradation test, test technology and method standard system. In recent years, Japan has successively established the Biodegradable Plastics Research Association and the Review Committee for the practical application of biodegradable plastics. Japan’s Ministry of International Trade and Industry has adopted biodegradable plastics as the “fourth kind of new material” after metal materials, inorganic materials, and polymer materials. European Bhre-Eurae has established a complete degradation assessment system for biodegradable plastics.

In recent years, R&D of fully biodegradable plastics has been the most active in developed countries. According to reports, in 1998, the total annual output of fully biodegradable plastics in the world was about 30,000 tons. By 2001, the output of the United States, Western Europe, and Japan had increased to about 70,000 tons. At present, the degradable products in foreign countries are mainly fully biodegradable plastics, which will continue to be the direction of future long-term industrial development.

Degradable plastics are mainly divided into photodegradable plastics, biodegradable plastics and photo-biologically degradable plastics according to their degradation mechanisms.

The photodegradation technologies that have been adopted abroad include synthetic and additive types. The former is the introduction of a photoactive group on the main chain of the olefin polymer, and the latter is the addition of a photosensitizing chemical aid to the polymer. The most studied are photodegradable polymers of ethylene copolymers. Studies have shown that when polyethylene is degraded to an oligomer with a molecular weight of less than 500, it can be absorbed and degraded by microorganisms in the soil and has good environmental safety. DuPont, Dow Chemical, Germany Bayer and other companies and the University of Toronto in Canada have used this technology to achieve industrial production.

Biodegradable plastics are high-molecular materials that can be rapidly degraded by the life activities of microorganisms in the natural environment. According to their degradation characteristics can be divided into completely biodegradable plastics and bio-destructive plastics. According to its source, it can be divided into natural polymer materials, microbial synthesis materials, chemical synthesis materials, and blended materials.

The natural polymer type is a biodegradable material prepared using natural polymer materials such as starch, cellulose, chitin, and protein. This type of material is rich in sources, completely biodegradable, and the product is safe and non-toxic, and has received increasing attention. Warner-Lambert Company of the United States has developed a new type of resin made from 70% amylopectin and 30% straight chain powder, which has good biodegradability and can replace various biodegradable materials used in agriculture. In Japan, a cellulose derivative and a deacetylated polysaccharide are compounded and a cast film is obtained. The strength of the film is similar to that of a polyethylene film and can be completely degraded in about two months. Although the natural polymer material is completely biodegradable, its thermal and mechanical properties are poor, and it cannot meet the performance requirements of engineering materials. Therefore, the current research direction is through the modification of natural polymers to obtain useful natural polymer degradation. plastic.