Degradable plastic package material alleviates "white pollution"

Using degradable polymer materials is one of the effective ways to reduce the pollution of traditional plastics. At present, all countries in the world are vigorously developing research and development of degradable plastics, and their application prospects are very broad.

At present, in daily life, biodegradable plastics can be used to make food packaging bags, packaging boxes, beverage bottles, cosmetic bottles, disposable ballpoint pens, garbage bags, travel articles, and leisure products. For example, a beverage bottle, a salad oil bottle, a can bottle, an organic solvent bottle, and the like can be produced from a polyvinyl alcohol-based raw material. Degradable plastics can be used in industrial and agricultural production for the manufacture of agricultural films, construction films, paper films (or paper supplies), pesticides and chemical fertilizer bags, forestry wood packaging materials.

Nowadays, photodegradable plastics are mainly used in the preparation of photodegradable agricultural plastics, photodegradable garbage bags, plastic packaging bags, disposable shopping bags, and photodegradable pull rings. In Western Europe, photodegradable plastics are mainly used to produce photodegradable garbage bags. , disposable shopping bags, photodegradable agricultural films, and photodegradable industrial packaging materials.

Biodegradable plastics are mainly used in the United States for the production of decomposition bags, shopping bags, and some biodegradable agricultural films; in Western Europe, biodegradable plastics are mainly used for biodegradable shampoo bottles, biodegradable waste bags, and some disposable shopping packages. Bags and so on. However, as far as the current level of technology is concerned, it is over-hyped with publicity that the use of these degradable materials to solve "white pollution" is obviously not appropriate because the application performance of these products is not ideal and there are still many problems.

There are problems First of all, the price of biodegradable polymer materials is high, so it is not easy to popularize and apply. For example, the degraded polypropylene snack box promoted by our country on the railway is 50%~80% higher than the original polystyrene foam snack box.

Second, the use of performance is still not satisfactory. At present, various types of starch plastics announced at home and abroad have generally mechanical properties. One of the main disadvantages of using performance is that the degradable plastics containing starch have poor water resistance and poor wet strength compared with the current plastics of the same type of application. When the water is exposed to water, the mechanical properties are greatly reduced, and the water resistance is precisely the current plastic in the Use the advantages of the process. For example, the photo-biodegradable polypropylene snack box has poor practicability, soft texture, easy deformation of the hot food, and high resource consumption compared with the existing polystyrene foam snack box. Styrofoam lunch boxes are 1 to 2 times larger. Polyvinyl alcohol-starch type biodegradable plastic is used as a disposable cushioning material for packaging, and its apparent density is slightly higher than that of ordinary polyvinyl alcohol buffer materials, and it is easy to shrink under the conditions of high temperature and high humidity, and is easily dissolved by water. Water soluble material.

Third, the problem of degradation control of degradable polymer materials remains to be solved. For example, medical applications require rapid degradation, but as packaging materials require a certain period of use; there is a considerable gap between accurate time control and complete and rapid degradation from practical requirements, especially for filled starch plastics. Most of them could not be degraded within one year. Although many tests have shown that their molecular weight has decreased significantly under the effect of ultraviolet light, this is a separate matter from practical requirements. In the United States, Europe and other developed countries, it is no longer acceptable to environmental organizations and the public.

Fourth, the evaluation methods for the biodegradability of polymer materials need to be improved. Due to the deteriorating performance of degradable plastics, there are many factors that limit the differences in the geographical environment, climate, soil composition, and waste disposal methods among countries. Therefore, what exactly is meant by degradation, whether its degradation time should be defined, and what is the degradation product, these issues have failed to reach a consensus, and its evaluation methods and standards are varied, and it takes time to establish a unified and complete evaluation method. .

Fifth, the use of biodegradable polymer materials will affect the recycling of polymer materials, and the use of biodegradable materials need to establish the appropriate basic processing facilities.

Development Trends With regard to the development trend of degradable materials, first of all, natural biopolymers such as cellulose, starch, and chitin should be used to make biodegradable plastics, and the functions and technologies for the improvement of natural polymers should be further developed.

Second, biodegradable plastics are synthesized using molecular design and fine synthesis techniques. Biodegradable plastics are prepared by the biodegradation mechanism of biodegradable synthetic polymers, and research and development of such polymers and existing general-purpose polymers, natural polymers, and microbial polymers are conducted.

Third, using biological genetic engineering, the use of green natural materials to produce degradable polymer materials. Such as cellulose, vegetable oil, tung oil, rosin and other natural substances. According to reports, British scientists have developed a rapeseed that can produce completely biodegradable plastics. They have used gene genetic technology to successfully implant three kinds of biological genes that can produce polymers into rapeseed. The seeds and leaves of rape grown from this rapeseed contain a large amount of polymer, which can be processed into various household plastic products and plastic pipes after being refined. If this kind of rape can be planted in large areas, it will greatly reduce the production cost of degradable plastics.

Fourth, biodegradable plastics are obtained through the cultivation of microorganisms, microorganisms capable of degrading macromolecular plastics are sought, new polymer materials are studied, and their synthesis mechanism is analyzed. At the same time, through the existing methods and genetic engineering methods to improve its productivity, research methods for efficient cultivation of microorganisms. At the same time, we must also study how to improve the performance of degradable plastics and reduce their cost.

Degradable plastics modification is also an important aspect. A photo-bio-degradable plastic film can be prepared by blending or grafting a general-purpose polymer (such as polyethylene and polypropylene) with a degradable polymer such as starch or cellulose. The plastic film is used for manufacturing disposable packaging materials and products, and can be completely degraded under the action of biology and light after use. In addition, the polyester and polyketone are blended and chemically modified with an oxidant such as hydrogen peroxide and peroxyacid to obtain a high-polymer plastic packaging material which has both a biodegradable function and a photodegradability, and can be used directly. In the production of fast food lunch boxes, garbage bags. It uses non-starch type photosensitizers and biodegradants. Its strength and transparency are superior to starch plastics, and its photodegradation performance is excellent. It can be embrittled within 50-100 days. Its degradation products can be further degraded by microorganisms such as molds and eventually become microorganisms. The carbon source returns to nature.

Although the currently-developed degradable plastics have not completely solved the problem of increasingly serious "white pollution", it is still an effective way to alleviate contradictions. Its appearance has not only expanded the function of plastics, eased the relationship between humans and the environment, but also demonstrated the power and prospects of biotechnology from synthetic technology, and will be an important area for the development of new materials in the 21st century.