Degradable plastic
Degradable plastic refers to a class of plastics whose products can meet the requirements of use, the performance is unchanged during the storage period, and after use, can be degraded into environmentally friendly substances under natural environmental conditions. Therefore, it is also called environmentally degradable plastic.
There are many new types of plastics: photodegradable plastics, biodegradable plastics, light, oxidative and biodegradable plastics, carbon dioxide-based biodegradable plastics, and thermoplastic starch resin-degradable plastics.
table of Contents
1 Concept
2 Degradation principle
3 Development Trend
4 Plastic classification
5 main uses
6 Research Status
▪ Widely used
▪ Environmental hygiene
▪ Biochemical reaction
▪ Non-degradable plastic hazards
▪ Development of degradable plastics
▪ The prospect of degradable plastics
▪ sustainable development
7 New plastics
8 Advantage analysis
9 Evaluation criteria
Concept editor
Polymer degradation refers to the process of polymerized macromolecular chain breaks caused by chemical and physical factors. The degradation process of polymers exposed to the environmental conditions of oxygen, water, radiation, chemicals, pollutants, mechanical forces, insects and other microorganisms, as well as microorganisms, is called environmental degradation. degradation
The molecular weight of the polymer is reduced, and the physical properties of the polymer material are reduced until the usability of the polymer material is lost. This phenomenon is also called aging degradation of the polymer material.
The aging degradation of a polymer is directly related to the stability of the polymer. Aging degradation of polymers shortens the service life of plastics. For this reason, since the advent of plastics, scientists have been committed to the research of anti-aging, that is, stabilization of such materials, in order to obtain highly stable polymer materials, and scientists in various countries are also using the polymer's aging degradation behavior Race to develop environmentally degradable plastics.
The main application fields of degradable plastic are: agricultural mulch film, various plastic packaging bags, garbage bags, shopping bags in shopping malls, and disposable tableware.
Degradation principleedit
The degradation process of environmentally degradable plastics mainly involves biodegradation, photodegradation and chemical degradation. These three major degradation processes have synergy, synergy and coherence. For example, photodegradation and oxide degradation often occur simultaneously and promote each other; biodegradation is more likely to occur after the photodegradation process.
Development Trend Editor
In 1997, the world's degradable plastics market is estimated to be about 20 million pounds with sales of $ 23 million; it is expected to grow by 35% by 2004. Degradable plastics found in the U.S. and Japanese markets include biodegradable polyesters such as polylactic acid, biodegradable PET, polybutene succinate / caproate, polyhydroxybutyrate / valerate, polyvinyl succinate , Polyester amines and polycaprolactones / mixtures; starch and mixtures thereof; and other plastics with additives that enhance the ability to degrade. The increase is due to an increase in the use of environmentally friendly plastics, and another reason is to reduce production costs. By expanding production and economic scale, manufacturers have reduced their prices. However, due to the high cost of degradable resins and the various plastics that have firmly occupied their markets, it is an obstacle for biodegradable plastics to enter the market. Its development trends are as follows:
1. According to different uses and environmental conditions, further deepening research, and through molecular design research, improving formulas, and developing timely and controllable environmentally degradable plastics have become key research topics in many countries.
2. Actively research and develop high-efficiency and inexpensive photosensitizers, oxidants, biological inducers, degradation promoters, stabilizers, etc., to further improve on-time controllability, rapid degradation and complete degradation after use.
3. Speed up the development of biodegradable plastics or ordinary plastics with starch, cellulose or inorganic material filling blending or alloying technology, and fully biodegradable plastics and natural materials coating and lamination technology are hot spots.
4. Hydrolysable plastics and edible plastics have attracted worldwide attention due to their special functions and uses, and have become another hot spot for environmentally-friendly materials.
5. In order to accelerate the development of degradable plastics, various countries are working to accelerate research and establish a unified definition, degradation mechanism, evaluation method and standard of degradable plastics.
6. Explore and cultivate strains that can degrade ordinary plastics, so that widely used ordinary plastics are easily degradable to meet environmental protection requirements. At the same time, great attention is given to the cultivation of biological plants that can produce polyester to reduce the cost of biodegradable plastics, which is conducive to popularization and application. degradation
Plastic classificationedit
Environmentally degradable plastics are a new type of plastic. The development of environmentally degradable plastics began in the 1970s. At that time, photodegradable plastics were mainly developed to solve the problem of environmental pollution caused by plastic waste, especially disposable plastic packaging products. By the 1980s, development and research turned to biodegradable plastics. Moreover, biodegradable plastics produced from renewable resources, such as plant starch and cellulose, and animal chitin, were used instead of petroleum. In addition, biodegradable plastics produced by microbial fermentation have also been developed. A class of biodegradable medical plastics, such as polylactic acid, which has already been clinically used, has also attracted people's attention. It is hoped that it can be used to solve the environmental pollution problems of plastics. However, whether such plastics are classified as environmentally degradable plastics or not With different opinions, the opinion of the Japan Society for Degradable Plastics does not consider it to be classified as environmentally degradable plastics. However, from the perspective of degradable plastics being a new type of plastic, biodegradable plastics can also be included. It may be useful to classify degradable plastics into environmental (natural) degradable plastics and biodegradable plastics from their uses. The latter has been used medically for surgical sutures, artificial bones, etc. The development and research of China's degradable plastics is basically synchronized with the world. However, research and development of degradable plastics in China began with agricultural mulch. China is a large agricultural country, and the consumption of mulch film ranks first in the world. In order to solve the damage caused by the residual mulch film accumulated on the farmland to the development of plant roots and affect the crop yield, as well as the problem of residual film hindering agricultural mechanization, Began the development of photodegradable plastic mulch film. Around 1990, biodegradable plastics filled with starch in general plastics appeared. At the same time, on the basis of photodegradable plastics, the development of mulching film with both photodegradation and biodegradation functions filled with starch . Various types of degradable mulch films are under development and are still in the stage of application demonstration and popularization. With the improvement of the living standards of the Chinese people, the environmental pollution caused by disposable plastic packaging products has become increasingly serious. For this reason, degradable plastic products such as garbage bags and shopping bags are also being actively developed for packaging, mainly disposable packaging. , Lunch box, etc.
Main use edit
The use of degradable plastics mainly has two fields: one is the field that used to use ordinary plastics. In these areas, it is difficult to collect the plastic products after use or consumption to cause harm to the environment, such as agricultural mulch film and disposable plastic packaging, and the second is the field of replacing other materials with plastic. The use of degradable plastics in these areas can bring convenience, such as golf course spikes and tropical rainforest plantation seedling fixing materials. Specific applications in:
1. Agriculture, forestry and fishery, mulching film, water-retaining material, seedling bowl, seedbed, rope net, pesticide and agricultural fertilizer slow-release material.
2. Packaging industry, shopping bags, garbage bags, compost bags, disposable lunch boxes, instant noodle bowls, cushioning packaging materials.
3. Sporting goods, golf course spikes and tees
4. Hygiene products, feminine hygiene products, baby diapers, medical mattresses, disposable razors.
5. Medical materials, bandages, clips, cotton swabs, gloves, drug release materials, surgical sutures and fracture fixation materials.
Research status editor
Wide range of applications
Synthetic polymer materials have been widely used in various fields. However, the used plastic waste has become a public and environmental hazard. Some developed countries have formulated regulations that restrict or ban the use of non-degradable plastics in certain places and require the use of degradable plastics. For this reason, governments of various countries and the plastics industry, while setting out effective measures for the disposal and recycling of waste plastics, attach great importance to research and development of degradable plastics. With the coordination and support of the government, degradable plastics have become a research in the international plastics industry. hot spot.
Environmental hygiene
Degradable plastic is generally considered to be a plastic that can be decomposed into low-molecular substances by sunlight or microorganisms in the soil. In addition to being degradable, it should also have properties that are easy to process and meet the requirements for use. The harmful effect of sunlight on polymer materials is the combined effect of ultraviolet light and oxygen, so it is called photo-oxidative degradation. Taking polyolefins as an example, photo-oxidation often causes polymer chain scission or cross-linking, and is accompanied by the formation of some oxygen-containing functional groups, such as ketones, carboxylic acids, peroxides, and alcohols. Its degradation mainly comes from the catalyst residues in the polymer and the initiation of peroxides and carbonyl groups introduced during processing.
Biochemical reaction
The cracking effect of low-light polymer mainly comes from the effects of biophysics, biochemistry and mold. Its sensitivity to the polymer depends on the structure of the polymer itself and the surrounding environment such as water, temperature, pH value and oxygen. According to the mechanism of degradation, degradable plastics can be divided into photodegradable plastics, biodegradable plastics, and photo / biodegradable plastics.
Non-degradable plastic hazard
Plastic is widely developed in many fields due to its advantages such as light weight, high strength, stable chemical properties, and low cost. The plastics industry has developed rapidly, and used plastics have not been properly disposed of, and plastics cause serious pollution to the natural environment. Non-degradable plastics are mostly made of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE), followed by high density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC ) Developed. These plastics are generally eventually disposed of as solid waste, causing pollutants such as acid rain to form in the air, which endangers our lives.
It is inevitable to study degradable plastics! Disposal of solid waste such as plastic will pollute the environment, bury it deep and invade the land, and burn it will pollute the air. These are not the fundamental solutions to the problem. The fundamental solution to the problem is to develop degradable plastics to replace non-degradable plastics.
Development of degradable plastics
Degradable plastic is a collective term for photodegradable plastic and biodegradable plastic. Developed countries began research on photodegradable plastics in the 1970s, and their concepts are relatively mature. Biodegradable began in the mid-1980s, developed rapidly, and already has its industrial products.
In China, research on photodegradable plastics began in the 1980s, and research on biodegradable plastics has only begun in recent years. There have been dozens of units engaged in this project in China, but the application is not large, and the promotion should be just started. China's degradable plastics are mainly concentrated in starch-filled products whose products have reached the same level as foreign products, but there is still some distance from industrial production.
The prospect of degradable plastics
First degradable plastics were developed to protect the environment. Has great significance. The excellent properties of degradable plastics are obvious and have broad development prospects. The research, development and production of degradable plastic masterbatches have a great promotion effect on the development and promotion of degradable plastics. Because the degradable plastic masterbatch is blended with the corresponding polymer to produce degradable plastic, there is no need to change the original plastic molding process. Has a wide range of practicability.
sustainable development
The research on degradable plastics is exactly adapted to China's sustainable development strategy and can adapt to the development of society. The use of polymer materials for chemical and biological methods to synthesize light / biodegradable plastics is our main research and development direction. We can use these polymer synthesis methods to synthesize the material we need-degradable plastic.
New plastic editor
Photodegradable plastic
It refers to a material that polymer chains decompose in order under the influence of ultraviolet rays. Most polymers do not absorb light with a wavelength above 285NM. However, if light-sensitive groups are added to the polymer or chemical additives with light-sensitive effects are added, the process of photooxidation can be accelerated, causing rapid degradation . According to the design principle and manufacturing method of photodegradable polymer molecules, it can be divided into synthetic photodegradable plastics and additive photodegradable plastics.
Copolymer photodegradable plastic was invented by DuPont of the United States, copolymerized by polyethylene (PE) and carbon monoxide, that is, E-CO copolymer, or copolymerized by polyethylene and vinyl copper, that is, GUILLET copolymer. To enhance the degradation of PE plastic. By changing the content of carbonyl groups in PE, the degradation period of this plastic can be controlled around 60 ~ 600 days. Later, carbonyl-containing copolymers such as polystyrene (PS), polypropylene (PP), polyvinyl chloride, and polyamide (PA) were developed. In some developed countries in Western countries, PE photodegradable film has been used as mulch film, food bags and garbage bags, and PP degradable film is also used in food packaging and cigarette production.
Additive type photodegradable plastic is to add a small amount of photoinitiator and other additives to the polymer. Typical photoinitiators or photosensitizers are aromatic ketones, aromatic amines, iron acetylacetonate, and 2-hydroxy-4 methylphenethyl Ketooxime, iron stearate, etc. Adding these photosensitizers to polymers such as PE, PP, PVC, and PS is feasible.
In recent years, the research on photodegradable polyethylene made from long-chain alkyl ferrocene derivative houses and the successful research of photodegradable PE plastic films using iron compounds as photosensitizers by the Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences have been completed. Photodegradable PE film with metal as photosensitizer developed by Dalian Plastics Research Institute.
Biodegradable plastic
From the perspective of the biodegradation process, it is divided into two categories: fully biodegradable and biodegradable plastics; from the perspective of preparation methods, it can be divided into four types: biofermentation synthesis, chemical synthesis, and the use of natural macromolecules or minerals from animals and plants.
Fully biodegradable plastics are easily degraded during chemical synthesis using aliphatic polyesters, polyvinyl alcohol (PVA), and polyethylene glycols. The biodegradable plastics are researched and developed using these polymers' easily biodegradable properties. Among them, the research on aliphatic polyesters is outstanding. Among the many aliphatic polyesters, polycaprolactone (PCL) is widely used. It is a thermoplastic crystalline polyester that can be hydrolyzed by lipase into small molecules and then further assimilated by microorganisms. The UCC company in the United States has been mass-produced and has been used in surgical products, mucous membranes, release agents and other products. After PCL and PHB are blended, biodegradable plastics can also be prepared. Aliphatic polyester and nylon undergo an amine exchange reaction to synthesize a polyacrylamide copolymer (CPAE). CPAE is a new type of biodegradable plastic.
In the synthesis of natural polymers from plants and animals, cellulose, starch, etc. from plants, chitosan, glucosamine, animal glue, and algae from marine life can be used to make valuable biodegradable plastic.
Chemical methods and natural polymer blending technology can also be used to synthesize degradable plastics. The main varieties are PHB / PCL, gelatinized starch / PCL and other products. Their main feature is that they can be completely degraded, and at the same time, their heat resistance, water resistance and cost are reduced through blending, making them a universal degradable plastic.
Biodegradable plastics are incomplete biodegradable plastics. They are mixed with biodegradable substances in olefin general-purpose plastics, causing the materials to lose their mechanical properties and shapes. Composting produces the same effects as biodegradable plastics. Low cost, this method has been adopted at home and abroad.
Aliphatic polyester biodegradable plastics are general-purpose plastics that are very thin and fibrous and are uniformly dispersed into biodegradable polyesters to make the copolymers biodegradable. Aliphatic universal plastics such as PE, PP, PS, P
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