The Defects and Countermeasures of Degradable Plastics in China

Plastics are widely used in all walks of life, especially packaging. Discarded plastic materials cannot or will not break down on their own, which not only affects the environment, but also causes damage to the ecology, agriculture, animal husbandry, soil, livestock and aquatic organisms. Common plastic wastes include: polyethylene, polypropylene, polyvinyl chloride, polyester film, packaging bags, packaging bottles, cups, plates, fast food boxes, cutlery containers, agricultural films, pipes, and automobiles, building materials accessories, and foaming Buffer liners, etc., in which packaging waste occupies the largest proportion.

In the 1990s, the international material community paid attention to research and development of environmental materials. "Environmental friendly materials", "environmental coordination materials" and "environmental ecology materials" are references to different schools in the international material community. The ultimate goal is to seek the coordinated development of materials and the environment.

Plastics that can reduce the pressure on the environment can be called environmentally friendly materials. It includes: plastic materials that are cost-effective, can be produced by clean methods, and can be environmentally-accepted. Therefore, the research and development of environment-friendly plastics is a systematic project and should be analyzed and judged by comprehensively utilizing the principles of product life cycle analysis. In this sense, degradable plastics are a variety of environmentally friendly plastic materials.

Standards and awareness of misunderstanding "white pollution" can not rely on degradable plastics to solve the treatment of disposable plastic packaging waste, to solve the "white pollution" problem, generally through the use of incineration and the use of degradable materials and other methods. Among them, recycling is an important way for countries to solve environmental problems caused by plastic waste. Plastic waste that is easy to recycle and has material recovery value should be recycled as much as possible. However, for those disposable plastic wastes that are difficult to recycle or have no recycling value, they should be degraded.

But "white pollution" cannot be cured by degradable plastics. Because degradation of plastics also requires a process, degradable plastics are not recycled and can also cause landscape pollution. Recycling is the premise of unified treatment and recycling.

The classification of degradable plastics is irrational At present, degradable plastics are generally divided into three categories: photodegradable plastics, biodegradable plastics, and biodegradable plastics. The compulsory local standards for DB343/35 biodegradable plastic films and packaging bags developed in Fujian Province have added a new category of “photodegradable and burnable” plastics, which has increased the classification of biodegradable plastics to four. This classification method distinguishes degradation plastics that use different conditions to promote plastic degradation in a certain sense, but it cannot fully include existing degradable plastics.

At present, new technologies such as thermal oxygen degradation, chemical degradation, light-induced light degradation, compost degradation, and acid-base degradation are emerging. It is not possible to limit the development of other technologies and the promotion of new technologies and new products according to the existing classifications. Degradable plastics may not meet the standards of the so-called “breakage retention rate” and “degradation rate” technical indicators for so-called photodegradation and biodegradation. Failure to meet the standard does not mean that the plastic has no degradation function.

“Degradation rate” is not the best representation of degradability. HJB12-2000 Environmental Labeling Specification for Packaged Products Technical Indicators Specifications for Biodegradable Plastics Degradation rate is measured using ASDM D5338-1996. The characterization means that the plastic is converted under certain environmental conditions. The carbon content of carbon dioxide is the percentage of the total carbon content in the plastic. This measurement method requires that the degraded plastic must contain organic substances that can be converted into carbon dioxide, such as carbohydrates, starches, proteins, and cellulose. According to the long-term testing experience of the Institute of Solid Waste of the Chinese Academy of Sciences, it is necessary to contain more than 20% starch in plastics to pass the biodegradation index of photo-biodegradable plastics with a degradation rate of >10. To achieve a degradation rate of >15 The biodegradability index of biodegradable plastic in % shall contain more than 30% of starch in the plastic. At present, there are not many companies that can add 20% or even 30% of starch to plastic films. Most of the samples sent to testing centers are either too thick to be sold in the market, or they are broken like a sponge. This film has no practical value at all. At present, few samples can be detected synchronously by biodegradation and mechanical properties.

In fact, biodegradable plastics do not necessarily have to be converted to carbon dioxide. “Biodegradation weightlessness” is a common phenomenon and it is more appropriate to describe the degree of degradation of plastics. As for the "degradation weight loss rate" of the experimental conditions, etc., can be further studied, mainly based on different degradable plastic varieties to develop different environmental conditions.

The use of waste and the treatment of degradable plastics are based on common plastics. Many environmentally friendly additives have been added to improve the coordination with the environment. From the current technology point of view, the degradation of the appearance and strength of degradable plastics is unavoidable, which is one of the important reasons why degradation of plastics is difficult to promote. Therefore, it is necessary for the public to change the concept of consumption and fully realize that plastic products that meet the national standard are acceptable.

In addition, the ultimate attribution of degradable plastics is to be associated with waste, so the formulation design of degradable plastics should be based on the comprehensive utilization and disposal of waste. At present, the main methods for the combined use and treatment of garbage are burial, composting, and burning. Therefore, the degradable plastic products can not only consider the two environmental conditions of light and biology in the formula design, but also take full account of various natural and man-made environmental conditions.

Development Principles and Development Goals of Degradable Plastics Conventional plastic resins are obtained by extrusion granulation using resin powders of petrochemical polymers with the addition of antioxidants, antioxidants, heat stabilizers, and anti-UV agents. At present, the environmentally degradable plastics that are researched and put into production at home and abroad are basically based on conventional plastic raw materials and added with degradable masterbatch, which not only consumes stabilizers and other materials, but also increases the cost and reduces the degradation performance. Coupled with the limited equipment conditions of environmental degradation plastics manufacturers, the manufacturers are scattered, and the quality of the degradative masterbatch produced in various places is uneven. Therefore, the quality of existing degradable plastics is often difficult to guarantee.

In addition, the direction of waste plastics is not the same, and the environmental conditions of exposure are different. The single-function degradable plastics can only work under certain environmental conditions and cannot fully utilize various environmental conditions and cannot adapt to the comprehensive treatment of waste.

Therefore, it is necessary to adjust and guide the research and development of the degradable plastics according to the direction of the comprehensive utilization of wastes and the management of them, and everything should be based on the comprehensive utilization and management of waste and the protection of the ecology.

The controllability and thoroughness of degradation of degradable plastics should maintain their proper performance during storage and use. When it is finished and its service life is discarded, under the sunlight, the degradable plastic will be cracked and broken up and the molecular weight will be reduced. When buried in the soil, microorganisms such as bacteria can multiply and erode on the degradable plastic and be gradually absorbed by the natural world. Affect the environmental purpose of the landscape. It can reduce the harm of “white pollution” and greatly reduce the amount of urban waste.

The ideal degradable plastic products must be prepared with appropriate degradation time according to the weather, season, and the amount of illumination in different regions. It can make the degradable film more stable in the initial photooxidation process, and a clear induction period appears. Photooxidation. In fact, the premise of the promotion and application of degradable plastics is to make the degradable film have a certain service life and achieve controlled photodegradation. Degradable plastics belong to high-tech products, and their production technology and quality control requirements are very strict, requiring the guidance of technical staff of professional research institutions.

How to ensure that the controllability and thoroughness of degradable plastics are the key to testing a certain technology and product, and technical receivers and government promotion departments should verify the controllability and thoroughness measures and indicators that the technology and manufacturers provide for protection against degradation. Each research unit and production unit should strengthen the degradation of various technologies.

Recent Research Results In recent years, the Research Institute of Environmental Materials of Fujian Normal University has carried out a number of research projects with certain characteristics, such as “combination of photosensitizers for r&d and comprehensive absorption of ultraviolet light” and “environmental performance of bioactive substances and inorganic minerals”. , “Development of biodegradable multi-functional plastics”, “Environmentally Reducible Resins”, “Acid-base degradable plastics”, “PVC Degradable Plastics Series Technology”, “Research on Degradation of Thermosetting Plastics”, and “Efficient Agricultural Environment Ecology "Development of Polymer Materials" and so on. Among them, the "composite photosensitizer" has been synthesized and screened for photosensitizers capable of absorbing different wavelengths of ultraviolet light, and has been effectively combined to make the degradable plastics undergo light-induced degradation after oxidization, thereby improving the thoroughness of degradation. “Special resin” uses resin powder produced by petrochemical without adding stabilizers. The main additives include photosensitizers, bioactive agents, nano-based inorganic materials, ultrafine inorganic materials, and the like. For plastics processing companies, the use of "special resin" methods to produce environmentally friendly materials, in addition to the use of "masterbatch method" compared to the former in addition to a more secure, more comprehensive environmental performance, will also greatly improve the finished product Rate, reduce the requirements for production equipment and testing equipment.