Current situation and development of the hottest d

Current situation and development of degradable plastics continued

2 Positioning of degradable plastics

in recent years, the international definition of degradable plastics has three aspects:

molecular aspect: plastic waste has a significant change in chemical structure or a significant decline in molecular weight in a relatively short time, and finally it is completely degraded into carbon dioxide and water

material properties: the internal mechanical properties of plastic waste decline in a short time, and its original application function is basically or completely lost

morphology: plastic waste breaks, collapses, and pulverizes in a relatively short time, becoming environmentally friendly or easily absorbed by the environment

by analyzing the above definition, it can be found that degradable plastics are not required to be completely degraded into carbon dioxide and water in a short time, but are required to be degraded in a short time to significantly change the original form of waste, and the degradation products are harmless to the environment

theoretically, the ideal degradation mode should be that plastic waste is degraded in a short time until the original form disappears, and then continue to undergo harmless degradation, and degrade to the final products carbon dioxide and water in a relatively short time. However, the development level of degradable plastics at home and abroad is far from reaching this level. Although fully biodegradable plastics can be degraded harmlessly, the degradation process is too affected by region, environment and climate, and the degradation time cannot be accurately controlled, and there are still some problems in use; For synthetic photodegradable plastics and ordinary plastics with degradation additives, not only the degradation time cannot be accurately controlled, but also the objective lens and eyepiece lens should be carefully removed. Whether the macromolecular chain can be further degraded after breaking into medium length molecular chain or short molecular chain, the degradation speed, and the toxic and side effects of degradation products on the environment in the process of further degradation need to be further studied. Therefore, it is unnecessary to require degradable plastics to achieve complete degradation

if it is required that the degradable plastics must be completely degraded, there are two situations. One is that the additive degradable plastics added with degradation additives must be added with a large amount of degradation additives from the history of the past few decades, which will bring cost problems. Another situation is to replace the original plastic directly molded products with fully biodegradable plastics or synthetic photodegradable plastics or their blends. Many such products have appeared abroad in recent years, but the price is high and it is difficult to apply and promote; The relatively successful alternative example in China is the fast food lunch box, but it also seems to have some problems; In addition, it must be noted that many plastic products cannot be simply replaced, such as EPS packaging materials. In recent years, many completely biodegradable foam substitutes at home and abroad have failed to replace EPS, and EPE and EPP granular materials abroad in recent two years have also failed to replace EPS

in the early years, foreign countries once paid attention to the development of fully degradable degradable plastics. In recent years, due to environmental pressure and cost pressure, they have shifted the focus to crumbling degradable plastics in order to reduce costs and facilitate popularization and application

to sum up, the degradability of degradable plastics and their products in China should be oriented at collapse degradation, and complete degradation should not be excluded. This will help bacterial plastics and synthetic degradable materials get rid of the dilemma of high cost and not easy to promote at present, is conducive to the low cost of degradable plastics, and is also conducive to the healthy and orderly development of the field of degradable plastics

3. Develop multi blend biodegradable plastics and speed up the development of biodegradable plastics

bacterial plastics and synthetic biodegradable plastics have been studied deeply in China in recent years. These materials have good degradation performance, but they are difficult to be popularized because of their high cost. Blending one or more of these plastics with ordinary plastics can not only basically maintain the mechanical properties and processing properties of ordinary plastics, which is convenient for popularization and application, but also help to improve the level of biodegradable plastic products through the application of new synthetic biodegradable materials, promote the development of biodegradable plastics, and help the research of synthetic polymer materials and bacterial plastics enter a virtuous cycle

4. Developing mineral filled degradable plastics is an important way to realize low-cost degradable plastics

for bulk products, realizing low-cost is the premise for the popularization and application of degradable plastics. On the premise that the material performance requirements are basically met, using a large proportion of mineral fillers can effectively reduce costs, and the process operation is simple. However, the filler does not play a direct role in degradation here. It must be initiated and promoted by other photodegradation additives, so that the yield point is difficult to identify degradation. The experimental results show that for additive photo biodegradable plastics, mineral fillers can promote the uniform degradation of plastic waste and shorten the degradation time; For polyolefin biodegradable plastics, secondary stretching during the molding process after filling can form countless tiny cracks on the surface and inside of the product, which are of great significance to promote the degradation of polyolefin biodegradable plastics

5. Conclusion

there is no doubt that degradable plastics is a promising field, which is in a period of vigorous development. The technical problems in degradable plastics need to be solved by the joint efforts of the whole industry. The problems existing in the development of degradable plastics and some abnormal phenomena should be gradually solved by the publicity and guidance of the plastic industry