The status and development of degradable plastics

2. Positioning of degradable plastics

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

On the molecular side: Plastic wastes undergo significant changes in chemical structure or have a significant decrease in molecular weight in a relatively short period of time, eventually degrading completely to carbon dioxide and water;

In respect of material properties, the plastics material will have decreased mechanical properties within a short period of time, and its original application functions will be lost or completely lost.

In terms of morphology, plastic waste breaks down, disintegrates, and pulverizes in a relatively short period of time and becomes a substance that is harmless to the environment or easily consumed by the environment.

By analyzing the above definition, it can be found that there is no requirement for degradable plastics to be completely degraded into carbon dioxide and water in a short period of time. Instead, it is required to degrade in a relatively short period of time to cause a significant change in the original form of the waste. The degradation product has no effect on the environment. harm.

In theory, the ideal mode of degradation should be that the plastic waste degrades to its original form in a short time and then continues harmless degradation, degrading to the final product carbon dioxide and water in a short period of time. However, the level of development of degradable plastics at home and abroad is still far from this level. Although fully biodegradable plastics can be harmlessly degraded, the degradation process is affected by the area, the environment, and the climate too much, and the degradation time cannot be accurately controlled, and there are still some problems in use; for synthetic photodegradable plastics, ordinary plastics added In the case of degradation aids, it is not only impossible to accurately control the degradation time. For the already degraded cases, whether the macromolecular chain breaks into a medium-length molecular chain or a short molecular chain can be further degraded, how is the degradation rate, and the degradation product is further degraded to the environment The toxic and side effects have yet to be further studied. It is therefore not necessary to require degradation of the plastic to achieve complete degradation.

If it is required that the degraded plastic must be completely degraded, then there are two cases. In one case, the addition of degradation aids to the additive-degrading plastics with the addition of the prodegradant must add a large amount of prodegradants, which brings about cost problems. In another case, all the plastic directly molded products are replaced with completely biodegradable plastics or synthetic photodegradable plastics or blends of the two. Such products have appeared in many foreign countries in recent years, but they are difficult to popularize due to high prices. Domestically, they are relatively successful. An alternative example is a fast food lunch box but it seems that there are certain problems; in addition, it must be noted that many plastic products cannot be simply replaced. For example, EPS packaging materials have not been replaced by many completely biodegradable foam substitutes at home and abroad in recent years. EPS, EPE, EPP particles that appeared abroad in the past two years have not been able to replace EPS.

In the past, foreign countries had paid attention to the development of fully degradable degradable plastics. In recent years, due to environmental pressure and cost pressures, the focus has shifted to disintegrated degradable plastics, so as to reduce costs and facilitate popularization and application.

In summary, the degradability of China's degradable plastics and their products should be positioned in a disintegration-type degradation, while not completely rejecting the degradation. In this way, it is beneficial to the bacteria plastics and synthetic degradable materials to get rid of the predicament that the current high cost is difficult to be promoted, which is beneficial to the cost reduction of degradable plastics, and is also conducive to the healthy and orderly development of degradable plastics.

3. Develop multi-complex biodegradable plastics to accelerate the development of biodegradable plastics

Bacterial plastics and synthetic biodegradable plastics have been studied in recent years in China. The degradation performance of these materials is good, but it is difficult to promote due to the high cost. The blending of one or more of these plastics with ordinary plastics can not only maintain the mechanical properties and processing performance of common plastics, but also facilitate the popularization and application, and facilitate the promotion of the level of biodegradable plastic products through the application of new synthetic biodegradable materials. The development of biodegradable plastics is conducive to the study of synthetic polymer materials and bacterial plastics entering a virtuous circle.

4. Development of mineral-filled degradable plastics is an important way to achieve low-cost degradable plastics

For bulk products, achieving low cost is the premise for the application of degradable plastics. Under the premise of basically satisfying the material performance requirements, the use of a large proportion of mineral fillers can effectively reduce the cost, and the process is simple. However, the filler does not play a direct role in the degradation here, and must be initiated and promoted by means of other light, biodegradable additives. The experimental results show that for additive light and biodegradable plastics, mineral fillers can promote the uniform degradation of plastic waste and shorten the degradation time; for polyolefin biodegradable plastics, after the filling, the secondary stretching can be performed during the molding process, and can be on the surface of the products. Numerous tiny gaps are formed inside and these gaps are important for promoting the degradation of polyolefin biodegradable plastics.

5. Conclusion

There is no doubt that degradable plastics is a promising field and is in a period of vigorous development. The technical problems in degradable plastics need to be resolved through joint efforts of the whole industry. The problems in the development of degradable plastics and some abnormal phenomena should be caused by the plastics industry. Conduct propaganda and guide the gradual solution.