Problems with degradable plastics

Degradable plastics, a brand-new technological approach to the management of plastic waste, has achieved satisfactory progress after years of research and development. Of course, although photodegradation and photo-biodegradable plastic products are simple to process and low in cost, they are difficult to be degraded in time, and they are not suitable for entering landfill systems. Starch-filled degradable plastics are difficult to process and their performance is not satisfactory. Fully biodegradable plastics have good degradation performance, but they are difficult to process, expensive, and sometimes controlled to degrade. They require comprehensive composting after use. In addition, more reasonable process recipes for degradable plastics and recycling of waste materials are used. The problem remains to be further improved and improved. Although there are still many problems in the degradation of polymer materials, due to the progress of degradation technology, related problems are gradually being solved and the market prospects are getting better and better. In order to make the degradable plastic technology have greater development on the basis of greater achievements, from the perspective of development trends, there are the following aspects worth further discussion and study in the future.

1. The practicality of degradable plastics such as disposable plastic film, packaging materials and tableware

Degradable plastic products such as disposable plastic film, packaging materials, and tableware can be used for practical research by adopting the comprehensive degradation technology of controlled photo-oxygen-biodegradable plastics filled with edible starch or inorganic minerals. The area of ​​China's coverable plastic film is 500 million mu and the dosage is up to 400,000 tons. It is more suitable to use low-cost photo-oxygen-biodegradable plastic film, and the thickness is 0.005mm-0.015.

The degradable plastic film of mm can also adopt the simple photo-oxygen degradation technology of plastics, but it must be controlled and degraded. Such as the Chinese Ministry of Agriculture and the General Assembly of Light Industry led the development of technical standards for degrading mulching films or countries and industries, and organized and promoted them in a planned way. This has profound implications for solving the problem of abandoned farmland polluting farmland and benefiting future generations. With regard to shopping bags, degradable plastic products such as foods, grocery bags, and cutlery, the degradation characteristics must reach HJBZ.

12-2000 "Technical Requirements for Environmental Labeling Products of Packaging Products", QB/T2461-1999 "Degradable polyethylene film for packaging", GB

18006.1-1999 "General technical conditions for disposable degradable tableware", HBC1-2001

"Disposable tableware environmental labeling product technical requirements". Moreover, it must be emphasized that it must not be discarded at will, but it must also be forced to recycle, regenerate or incinerate the recovered energy.

2. Researching fully biodegradable plastics is an important development trend of degradable plastics

From the point of view of protecting ecological balance, it is urgent to study completely biodegradable plastics. In particular, biodegradable plastics with simple synthetic methods, reasonable processing processes, and low cost are an important research topic for biodegradable plastics. Non-returnable medical plastic products such as stitches, sutures, syringes, and infusion bags, disposable plastic products such as garbage bags, compost bags, pesticide bottles, cosmetic containers, diapers, and sanitary napkins for women should be used at a low cost. Biodegradation technology. For products such as garbage bags, compost bags, fertilizer bags, etc., high-quality, lower-cost, fully biodegradable plastics filled with starch or inorganic minerals can be studied to meet the needs of the market.

3. Use natural recyclable degradable materials as much as possible

According to the latest research report of the International Biodegradable Polymer Association (IBAW), between 2001 and 2003, the use of biodegradable plastics worldwide has doubled, and the total use has risen to 40,000 tons/year. IBAW states that although this figure also includes petroleum-based biodegradable materials, petroleum resources are now becoming increasingly scarce. As long as the technology permits, producers will use natural, recyclable materials as much as possible. Biodegradable plastics currently made from starch and vegetable oils have dominated the market. Recent surveys conducted in several countries show that consumers are very interested in this type of packaging material, and more interestingly, consumers are willing to pay more for this. Recently, a survey conducted by Grapentine Company, a US market research organization, found that 41% of American consumers and 59% of European consumers are eager to purchase foods packaged in biodegradable plastics made of natural materials. About 77% of European consumers are willing to pay 5 cents more for this, and 74% of American consumers are willing to pay 10 cents more. IBAW predicts that the share of natural biodegradable plastics in the biodegradable plastics market will continue to rise, especially under the current high oil prices.

4. Thermoplastic starch resin is the most promising fully biodegradable plastic

The starch molecules are allosterically and disordered to form a thermoplastic starch resin, followed by a small amount of additives such as plasticizers, so-called full starch plastics. The starch content is above 90%, and the small amount of other substances added are also non-toxic and can be completely degraded, so the whole starch is truly a fully degradable plastic. Almost all plastic processing methods can be applied to the processing of whole starch plastics. All-starch plastic is currently considered as the most promising fully biodegradable plastic at home and abroad. Sumitomo Corporation, Japan, United States Wanler

Lambert and Italy's Ferruzzi announced that they have successfully developed full-starch plastics with a starch content of 90% to 100%. The product can be completely biodegraded in 1 year without leaving any traces and pollution, and can be used to make various containers and films. And garbage bags and so on. The Battelle Research Institute in Germany developed a biodegradable plastic with modified green pea starch with a high linear content, which can be processed and formed by conventional methods. As a substitute for PVC, it can be completely degraded in a moist natural environment.

5. Carbon dioxide-based biodegradable plastics are currently research projects with broad development prospects

Japan's Inoue has found that carbon dioxide can undergo ring-opening polymerization with epoxides to form aliphatic polycarbonate (APC), which is the most promising CO2 copolymer to date. Takanashi et al. used a terpolymer of carbon dioxide, propylene oxide, and an ester-containing epoxide as a drug release agent. Masahiro et al. used the method of evaporating solvent to prepare PPC microspheres as the carrier of the drug sustained-release system, and studied the factors affecting the release rate of the system, such as the molecular weight of PPC, the drug content, and the like. The results showed that with the decrease of the diameter of the microspheres or the increase of the drug concentration, the drug release rate increased, but the drug release rate and biodegradability were independent of the molecular weight of the copolymer. The morphology of the microspheres before and after drug release was observed by SEM, and the PPC was confirmed. Microspheres support long-acting, uniform release of drugs. U.S. experts adopted a new technology that uses special zinc catalysts to mix and copolymerize carbon dioxide and ethylene oxide (or propylene oxide) in certain proportions to produce plastic packaging materials with new features. The carbon dioxide-based complete biodegradable plastics project implemented by China Jilin Group Corporation and the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, has been listed in the National 863 Research Program. It is a new high-tech environmental protection material research and development project with broad development prospects.

6. Definition of degradable plastics and evaluation methods are the basis for the promotion of degradable plastics

However, the world’s developed countries, especially the United States, have also done a lot of research. At present, ASTM has announced the following test standards: Biodegradable plastics related evaluation test standards, ASTM D5209-92, ASTM D5210-92, ASTM D5247-92, ASTM

D5271-92, ASTM D5338-92. Photodegradable plastics related evaluation test standards, ASTM D5071-91, ASTM D5208-91, ASTM

D3826-92. Environmental safety related evaluation test standard, ASTM D5152-91. At present, China has announced the relevant test standards are as follows: GB18006.1-1999

"General technical conditions for disposable degradable tableware", GB/T18006.2-1999 "Test method for degradation performance of disposable degradable tableware", HJBZ

12-2000 "Technical Requirements for Environmental Labeling Products of Packaging Products", HBC1-2001 "Technical Requirements for Environmental Labeling Products for Disposable Tableware", QB/T2461-1999

"Degradable polyethylene film for packaging". In the future, reference will still be made to the relevant testing standards of developed countries and China, combined with the market promotion of various types of degradable plastic products, and the research on the definition and evaluation methods of degradable plastics will be conducted in depth to continuously improve and improve relevant test standards. This is the promotion of degradable plastic products. The foundation and industrialization of the premise.