1. Definition

Degradable plastic refers to a kind of plastic whose products have various properties that can meet the requirements of use. The performance remains unchanged during the storage period. After use, it can degrade into environmentally harmless materials under natural environmental conditions. Therefore, it is also It is called environmentally degradable plastic.

Polymer degradation refers to the process of breaking the polymerized macromolecular ingots caused by chemical and physical factors. The polymer is exposed to oxygen, water, heat, light, radiation, chemicals, pollutants, and mechanical forces. The degradation process of macromolecular chain breaking under environmental conditions such as insects and microorganisms is called environmental degradation. Degradation reduces the molecular weight of the polymer, and the physical properties of the polymer material decrease until the polymer material loses its usability. This phenomenon is also called the aging degradation of the polymer material.

Both natural polymers and synthetic polymers will degrade when exposed to environmental conditions. However, under the same environmental conditions, the degradation sensitivity of various polymers, especially synthetic polymers, is very different. Therefore, various polymers The degradability of polyvinyl alcohol is also different. For example, polypropylene is easy to degrade under light oxygen environmental conditions, while polystyrene is difficult to degrade under the same environmental conditions, and polyvinyl alcohol is easier to degrade under environmental conditions where certain microorganisms exist. However, polyethylene, polypropylene, and polystyrene are difficult to degrade under the same environmental conditions.

The degradation process of environmentally degradable plastics mainly involves biodegradation, photodegradation and chemical degradation. Moreover, these three main degradation processes have synergistic, synergistic and coherent effects with each other. For example, photodegradation and oxide degradation often proceed simultaneously and promote each other; biodegradation is more likely to occur after the photodegradation process.

"The aging degradation of the polymer is directly related to the stability of the polymer. The aging degradation of polymers shortens the service life of plastics. For this reason, since the advent of plastics, scientists have devoted themselves to the anti-aging of such materials, that is, the study of stabilization, in order to obtain high-stability polymer materials. At present, scientists in various countries are also using the aging degradation of polymers. Behaviors compete to develop environmentally degradable plastics.

2. Classification

Environmentally degradable plastics are a new type of plastic

The development of environmentally degradable plastics abroad began in the 1970s. At that time, the main development of photodegradable plastics was to solve the environmental pollution caused by plastic waste, especially disposable plastic packaging products. By the 1980s, development and research turned to biodegradation. Plastics are the mainstay, and biodegradable plastics that use renewable resources, such as plant starch and cellulose, and animal chitin as raw materials instead of petroleum, have emerged. In addition, biodegradable plastics produced by microbial fermentation have also been developed.

A class of biodegradable medical plastics that have been clinically used, such as polylactic acid, has also attracted people’s attention. It is hoped that it can be used to solve the environmental pollution problem of plastics. However, whether this type of plastics is classified as environmentally degradable plastics is still There are different opinions, and the opinions of the Japan Degradable Plastics Research Association believe that it cannot be classified as environmentally degradable plastics. However, considering that degradable plastics are a new type of plastics, biodegradable plastics should also be included, and degradable plastics may be classified into environmental (natural) degradable plastics and biological (environmental) degradable plastics. The latter has been used in medicine for surgical sutures and artificial bones.

The development and research of biodegradable plastics in China is basically synchronized with the world. However, the research and development of degradable plastics in China began with agricultural mulch. China is a large agricultural country, and the consumption of mulch film is the largest in the world. In order to solve the problem that the residual mulch film accumulated in farmland causes damage to plant root development and affects crop yields, as well as the problem of residual film hindering the operation of agricultural machinery and farming operations, it was in the 1970s. Started the development of photodegradable plastic mulch film. Around 1990, biodegradable plastics with starch filled in general plastics appeared. At the same time, on the basis of photodegradable plastics, a mulch film with both photodegradable and biodegradable functions filled with starch was developed. . At present, various degradable mulch films are under development and are still in the stage of application demonstration and promotion. In recent years, with the improvement of the living standards of the Chinese people, the environmental pollution caused by disposable plastic packaging products has become more and more serious. For this reason, we are also actively developing degradable plastic products for packaging, mainly disposable packaging, such as garbage bags. Shopping bags, lunch boxes, etc.

Three, use

There are two main uses of degradable plastics: one is the original use of ordinary plastics. In these fields, it is difficult to collect plastic products after use or consumption, such as agricultural mulch film and disposable plastic packaging, which cause harm to the environment. The second is the field where plastics replace other materials. The use of degradable plastics in these fields can bring convenience, such as golf studs and seedling fixing materials for tropical rainforest afforestation. The specific application areas are as follows:

1. Agriculture, forestry and fishery, mulching film, water-retaining materials, nursery bowls, seedbeds, rope nets, pesticides and fertilizer slow-release materials.

2. Packaging industry, shopping bags, garbage bags, compost bags, disposable lunch boxes, instant noodle bowls, cushioning packaging materials

3. Daily miscellaneous goods, disposable tableware (knife, fork, chopsticks) toys, disposable gloves, disposable tablecloths.

4. Sporting goods, golf studs and tees

5. Hygiene products, feminine hygiene products, baby diapers, medical mattresses, disposable shavers.

6. ​​Medical materials, bandages, clips, small sticks for cotton swabs, gloves, drug release materials, and surgical sutures and fracture fixation materials.