Development status and trend forecast of degradable plasticsDevelopment status and trend forecast of degradable plastics
With the increasing awareness of environmental protection, taking the path of healthy and ecological sustainable development has become the best choice for the packaging industry. As the most widely used plastic packaging material, degradability has become a trend.
According to the different principles, degradable plastic materials are divided into the following three categories: biodegradable plastics, photodegradable plastics and other degradable plastics.
Biodegradable plastic packaging materials
Biodegradable materials refer to materials that can be degraded by natural microorganisms such as bacteria and fungi that interact with algae. The material can basically be completely decomposed by environmental microorganisms, and becomes carbon dioxide and water or methane and water after decomposition. The products of biodegradable packaging materials can participate in the carbon and nitrogen cycle in nature. Carbon and nitrogen elements can not only form the basic skeleton of organisms, but also realize the metabolism of organisms through their own biochemical reactions. Therefore, the biodegradable plastic packaging material is an environmentally friendly material.
Light-degradable plastic packaging materials
Light-degradable plastic packaging materials refer to materials that will automatically degrade under the action of light. The reaction mechanism is that plastics will absorb ultraviolet rays in the sun, which will reduce the bond energy, which will break the long polymer chains, and the large molecules will become small molecules. The small molecules will continue to undergo oxidation reactions, and the free radicals will undergo chain scission. The molecular fragments are completely oxidized by the air. Photodegradable plastics are divided into copolymer type and additive type. Copolymerization plastics are plastics formed by the copolymerization of monomers such as carbon monoxide or other olefins.
The use of chromophoric groups and weak bonds resembling carbonyl groups on the polymer chain makes it more unstable under light conditions, thereby achieving photodegradation. The additive type is to add benzophenone and other light-sensitive photosensitizers to ordinary plastics, so that it can absorb light with a wavelength of 300nm, promote dehydrogenation between molecules, continuously reduce molecular weight, and finally achieve complete degradation. The necessary condition for the degradation of photodegradable plastics is that there is sufficient light, that is, sufficient ultraviolet light. When the light or ultraviolet light is insufficient, the material is difficult to degrade, and the reaction conditions are relatively harsh.
Other degradable plastics
With the development of society, medical and health care has become a hot topic. The treatment of medical waste has also been paid more and more attention. Water-absorbent substances are added to it, and when the medical waste is thrown into the water after use, it will be completely dissolved in the water. Common medical gloves are treated in this way.
Development prospects of intrinsically flame-retardant polymer materials
At this stage, the main method of preparing flame-retardant polymer materials in my country is to use physical and mechanical methods and add flame retardants to ensure the realization of flame-retardant polymer materials. Although this method used in my country is very convenient, However, there are still many problems in the actual preparation process, such as the large dosage of flame retardant. In addition, the addition of flame retardants to polymer materials can directly have an extremely serious impact on the mechanical and physical and chemical properties of the matrix polymer, especially processing properties, electrical and mechanical properties.
At the same time, the stability of the flame retardant in the material is poor, which makes it extremely easy to lose during the use of it, which will not only pollute the environment, but also cause a serious waste of resources.
And because of the high flame retardancy of bromine and chlorine flame retardants, they continue to be widely used. However, relevant research has fully shown that bromine flame retardants will produce a large amount of flame retardant in the flame retardant process. The toxic gas not only poses an extremely serious threat to the environment and people’s life safety, but also greatly reduces the UV resistance of the flame-retardant matrix material, thus prompting people to pay more and more attention to the caused problem.
Therefore, in order to ensure that its existing shortcomings are effectively compensated, relevant researchers can successfully synthesize a series of new polymer materials with high flame retardant properties through the use of chemical reaction methods. On the one hand, select flame retardants and polymers with active originals, and start to prepare flame retardant polymers by using rearrangement or polycondensation. On the other hand, the atoms with flame-retardant properties are selected, and the new intrinsic flame-retardant polymer materials are directly synthesized.
In view of the current problems of degradable plastic packaging materials, the future research process should pay special attention to the following perspectives:
reduce manufacturing cost
Cost issues have always been an important indicator of whether products can be applied to the market on a large scale. In the future research process, we can reduce the cost of degradable plastic packaging materials by increasing the proportion of cheap raw materials, and reduce degradable plastics by optimizing and improving processes. The cost of packaging materials in the production process. Reduce costs from both the source and the production process.
Improve degradation effect
Photo-biodegradable plastics have the dual properties of photodegradable plastics and biodegradable plastics. Compared with photodegradable plastics, it is not restricted by light intensity and ultraviolet rays. Compared with biodegradable plastics, its process is much simpler. Researchers add two kinds of inducers to make it have excellent performance. That is, the biodegradation agent starch and the controllable photodegradation photosensitizer that induces the photochemical reaction, and some degrading agents.
Among them, the photosensitizer with controllable light degradation is relatively stable before the prescribed induction period, does not degrade the plastic, and has an ideal controllable light decomposition curve. During the induction period, the mechanical properties of the plastic remain above 80%. After reaching the service period, the mechanical properties decline rapidly. It is also possible to adjust the concentration ratio to decompose the plastic into fragments at regular intervals, and then under the combined action of the automatic oxidant and microorganisms on the starch, this material will be quickly decomposed.
Research new auxiliary products
Constantly explore to improve the composition ratio of biodegradable plastic packaging materials, make them more scientific, and improve their performance through the addition of additives. For example, by adding stabilizers to improve the stability of light-degradable plastic packaging materials, so that they are less affected by the external environment, and can be degraded even under conditions of weak light or ultraviolet light.
Although researchers have reached a high level of research on degradable plastic packaging, the following problems still exist at this stage:
Compared with ordinary plastics, degradable plastics often add certain chemicals to make them degrade when exposed to light and water. Every step from design to application increases the cost of plastics. Affected by environmental awareness and consumption habits, high-cost biodegradable plastics are still difficult to popularize.
Biodegradable plastic packaging materials are restricted by their degradability, and their performance is far lower than ordinary plastics to a certain extent. For example, after shopping in the supermarket, we have certain requirements for the load-bearing performance of plastic bags, and poor load-bearing performance is precisely a common defect of biodegradable plastics. Biodegradable plastics often have the characteristics of low transparency, which limits its application scope to a certain extent. In the actual selection process, consumers tend to pay more attention to its performance and less attention to processing problems after use.
At present, many plastic packaging bags on the market are marked with the word "degradable". And what exactly is a degradable material? How to define it scientifically and accurately? What is the time limit for degradability? Will it be degraded in advance before being used by the final consumer, which will affect the performance of the original packaging? Since there is no scientific and objective definition of this series of problems, there are many standards for degradable plastic packaging materials.
Take light-degradable plastic packaging materials as an example. In the actual process, light is an uncontrollable factor. When the material is buried in the soil, it is not degradable, and its performance different from ordinary plastic cannot be displayed. Before the product reaches the consumer, if it experiences strong light during transportation, the packaging will decompose, which will affect the content. The above factors cause the overall performance of photodegradable plastic packaging materials to be low. The most important thing is that our original intention of studying this material is to protect the environment, and we are still unclear on whether the products after photodegradation are harmful to the environment.
With the implementation of the "plastic ban", the development of new energy vehicles, the rise of 5G communications and the implementation of the sharing economy, the performance requirements of materials such as strength, temperature resistance, weather resistance, and low dielectric properties have increased, and the application of plastic materials with high standards With rapid growth in demand, differentiated high-end modified plastics will usher in the spring of development.