Foreword
The appearance of degradable plastics is to solve the white pollution caused by plastic waste. In the past 20 years, a lot of efforts have been made in theoretical research, material research, product development and application, publicity and promotion, and formulation of standards in the field of degradable plastics. Today it has achieved results: The concept of degradable plastics has been generally accepted and accepted by the whole society. A large number of biodegradable plastic products have been used. The amount of some products has already reached a certain scale. The research basis for many years has been the development of today's degradable plastic product development. Actively, the product development cycle is shortening, and a series of relevant standards have played an important role in regulating the degradation of plastic products. The pattern of degradable plastics has taken shape. The research and application of degradable plastics in China started later, but developed rapidly, especially in the last five years, forming a pattern of degradable plastic film, plastic film degradable masterbatch, and degradable fast-food lunchbox as the leader. It can be considered that degradable plastics has developed from a research direction into a new industry. î™î€‚
1. Development status and problems of degradable plastics
1.1 1 Status of Degradable Plastics
Degradable plastics can be divided into biodegradable plastics, photodegradable plastics, and light/biodegradable plastics.
Biodegradable plastics can be divided into completely biodegradable plastics and collapsed biodegradable plastics.
Fully biodegradable plastics include bacterial plastics, synthetic polymer materials (PVA, polylactic acid, etc.), natural polymer materials (starch, cellulose, and other polysaccharide materials). The former two are currently more expensive, while the latter are low in cost but performance. difference.
The collapsed biodegradable plastics include starch-filled plastics, cellulose-filled plastics, mineral-filled biodegradable plastics, and masterbatch-added biodegradable plastics.
(1) Domestic and Foreign Situations
The research focus on biodegradable plastics at home and abroad focuses on completely biodegradable plastics. In product use, starch-filled plastics, general-purpose plastics and synthetic degradable plastics are blended in foreign countries, and starch and synthetic degradable plastics are mainly blended; domestic natural polymer materials (mainly used for fast food lunch boxes) and starch-filled masterbatches are used in China. (Mainly used for plastic film) mainly. From the perspective of product degradation characteristics, foreign products are both fully degradable and disintegrated, with more disintegrating types; domestic products are mainly biodegradable in terms of biodegradable fast food lunch boxes, and mainly disintegrated in the field film. Other products are available in various situations but with much less.
Photodegradable plastic
Photodegradable plastics are classified into synthetic photodegradable plastics and additive photodegradable plastics. In the former, oxygen-containing functional groups are introduced into macromolecular main chains or branches during resin synthesis, and the latter adds photosensitizers or transition metal networks to common plastics. Compound. The research and application of synthetic and additive-type photodegradable plastics in foreign countries are quite similar. The technology is relatively mature and the development is stable. The domestic research and application are mainly focused on additive photodegradable plastics, and the technical level is comparable to that of foreign countries.
Light/biodegradable plastic
Light/biodegradable plastics combine photodegradation with biodegradation in order to increase the efficiency of degradation and the controllability of degradation. Light/biodegradable plastics are divided into two major categories. One is a blend of synthetic photodegradable plastics and completely biodegradable plastics, and the other is a blend of light/biodegradable masterbatches added to ordinary plastics. In China, since synthetic photodegradable plastics have not yet been mass-produced, they are mainly masterbatches. In recent years, there has been a high demand for photo/biologically degradable plastics in the country, and various types of degraded products have been developed with double degradation types.
Degradation and complete degradation of plastics
For the degradation-degrading and complete degradation of degraded plastics, we define it as: After plastic waste degrades and loses its original shape in a relatively short period of time, it takes a long time to degrade to carbon dioxide and water. Disintegrated degradation, such as the ability to further degrade into carbon dioxide and water in a relatively short period of time, is referred to as complete degradation. Judging from the overall situation, China's degradation of plastic products in the variety of disintegrated degradation products are more, but many companies dare not admit that their products are disintegrated degradation, due to public opinion, a few years ago the public opinion has been broken Degradable plastic basically negated.
1.2 Problems in the Development of Degradable Plastics in China
(1) The accuracy of degradation time control is poor;
(2) High product cost;
(3) Public opinion advocates the complete degradation of plastics and the dismantling of degraded plastics;
(4) Public opinion was misleading and there was a phenomenon that other materials were used instead of plastics to solve white pollution, and the development of degradable plastics once fell into the error zone.
Among the above problems, except that the control of degradation time needs to be solved step by step both at home and abroad, the core of the remaining problems is that the concept of degradable plastics is ambiguous. Therefore, the definition of degradable plastics should be clarified, and degraded plastic products should be clearly positioned. (to be continued)