Definition, classification and use of degradable plastics

First, the definition

Degradable plastics refers to a class of plastics whose properties can meet the requirements of use, remain unchanged during the shelf life, and can be degraded into environmentally harmless substances under natural environmental conditions after use. Therefore, it is also It is called environmentally degradable plastic.

Degradation of a polymer refers to the process of breaking a polymerized large molecule ingot due to chemical and physical factors. The polymer is exposed to oxygen, water, thermal light, radiation, chemicals, contaminants, mechanical forces. Degradation of macromolecular strand breaks under environmental conditions such as insects and other animals and microorganisms is called environmental degradation. Degradation degrades the molecular weight of the polymer and decreases the physical properties of the polymer material until the polymer material loses its usability. This phenomenon is also referred to as degradation degradation of the polymer material.

Both natural and synthetic polymers degrade under ambient conditions. However, under the same environmental conditions, the degradation sensitivities of various polymers, especially synthetic polymers, are very different. Thus, various polymers The solvability is also different. For example, polypropylene is easily degraded under photo-oxygen conditions, and polystyrene is difficult to degrade under the same environmental conditions. Polyvinyl alcohol is more easily degraded in the presence of certain microorganisms. While polyethylene, polypropylene, and polystyrene are difficult to degrade under the same environmental conditions.

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

Aging degradation of the polymer is directly related to the stability of the polymer. Aging degradation of polymers shortens the useful life of plastics. For this reason, since the advent of plastics, scientists have been working on the anti-aging of these materials, that is, stabilizing research to obtain highly stable polymer materials. At present, scientists in various countries are also using the aging degradation of polymers. Behavioural development of degradable plastics.

Second, classification

Environmentally degradable plastics are a new class of plastics

The development of environmentally degradable plastics abroad began in the 1970s, when light-degradable plastics were mainly developed to solve the environmental pollution problems caused by plastic waste, especially disposable plastic packaging products. By the 1980s, development research turned to biodegradation. Plastics are predominant, and there are also biodegradable plastics that are produced using raw materials such as vegetable starch and cellulose, and animal chitin as raw materials without using petroleum. In addition, biodegradable plastics produced by microbial fermentation have also been developed.

A class of medical plastics that have been clinically used for biodegradation, such as polylactic acid, has also attracted people's attention, hoping to use it to solve the problem of environmental pollution of plastics, but whether such plastics are classified as environmentally degradable plastics. There are different opinions. The opinion of the Japan Decomposing Plastics Research Association that it cannot be classified as environmental degradation plastics. However, from the perspective of degradable plastics being a new class of plastics, biodegradable plastics should also be included. It may be desirable to classify degradable plastics from use into environmental (natural) degradable plastics and biodegradable (environmentally) degradable plastics. The latter has been used medically for surgical sutures, artificial bones, and the like.

The development and research of degradable plastics in China is basically in sync with the world. However, the research and development of China's degradable plastics began with agricultural mulch. China is a large agricultural country with the largest amount of mulch in the world. It has affected crop yields by solving the damage caused by the residual plastic film accumulated in farmland on the development of plant roots, and the obstruction of residual film on agricultural machinery and farming operations. In the 1970s, The development of photodegradable plastic mulches was started. Before and after 1990, biodegradable plastics filled with starch were used. At the same time, on the basis of photodegradable plastics, mulching films with both photodegradation and biodegradability were developed. . At present, all kinds of degraded plastic film are under development, and they 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 problem of environmental pollution caused by disposable plastic packaging products has become increasingly serious. For this reason, it is also actively developing degradable plastic products such as garbage bags that are mainly used for packaging. Shopping bags, lunch boxes, etc.

Third, use

The use of degradable plastics has two main areas: The first is the use of ordinary plastics in the field. In these areas, the use or consumption of plastic products is difficult to collect back to the environment, such as agricultural plastic film and disposable plastic packaging, and the second is the field of plastic instead of other materials. The use of degradable plastics in these areas can be facilitated, such as the use of ball studs for golf courses, seedlings for seedlings of tropical rain forests. Specific application areas are as follows:

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

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

3. Daily groceries, disposable tableware (knives, forks, chopsticks) toys, disposable gloves, one-time meal cloth.

4. Sporting Goods, Golf Ball Studs and Tees

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

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