Development and status quo of green packaging materials Since the new century, my country’s economy has continued to develop at a high speed, but it is also facing some contradictions while economic development. On the one hand, due to advances in nuclear energy technology, information technology, biotechnology and advanced manufacturing technology in the last century, human society has accumulated unprecedentedly strong material wealth and spiritual civilization. People pursue a higher quality of life and hope to live a healthier life. Safer and longer life. On the other hand, people are facing the most serious crises in history, such as resource shortages, energy depletion, environmental pollution, deterioration of natural ecology (ice caps, grasslands, wetlands, biodiversity reduction, desertification, acid rain, sandstorms, Chihu, drought Frequent, greenhouse effect, El Niño climate abnormality), these all threaten the survival of mankind. Based on the above-mentioned contradictions, the concept of sustainable development is increasingly being mentioned on the agenda.
Sustainable development refers to development that can meet the needs of contemporary people without harming the needs of future generations. In other words, it refers to the coordinated development of economy, society, resources, and environmental protection. They are an inseparable system that not only achieves the goal of economic development, but also protects the atmosphere, fresh water, ocean, land, and land that humans depend on for survival. Natural resources such as forests and the environment enable future generations to develop sustainably and live and work in peace and contentment. Global sustainable development includes five main points: development assistance, clean water, green trade, energy development and environmental protection. Sustainable development and environmental protection are not only related, but not the same. Environmental protection is an important aspect of sustainable development. This article wants to start with environmental protection and talk about the development and current situation of plastic packaging materials that we cannot do without from the perspective of sustainable development. In just over 20 years since its entry into my country, the output of plastics has ranked fourth in the world. Plastic products are difficult to degrade, and the serious harm of its “white pollution” has caused immeasurable losses to society and the environment. Every year, a large amount of land is wasted to bury plastic garbage. If it is not controlled, it will bring great harm to our children and grandchildren, to the earth we live on, and affect the sustainable development of the world.
Therefore, looking for new resources for sustainable development, exploring and researching environmentally friendly green packaging materials has become an important topic for the sustainable development of human society. From the mid-1980s to the present, scientific and technological workers from all over the world have done a lot of exploratory work from the recycling of plastic packaging materials to the search for new materials to replace non-degradable plastic packaging materials. According to the different degradation methods of plastics used for packaging materials, currently, it is mainly divided into five categories: double-degradable plastics, polypropylene, grass fibers, paper products, and fully biodegradable packaging materials.
1. Double-degradable plastic: adding starch to plastic is called biodegradable plastic, adding photodegradation initiator is called photodegradable plastic, and adding starch and photodegradation initiator at the same time is called double-degradable plastic. Since the dual-degradable plastic cannot completely degrade the component state, it can only be degraded into small fragments or powder, and the damage to the ecological environment cannot be weakened at all, but even worse. The photosensitizers in light-degradable plastics and double-degradable plastics have varying degrees of toxicity, and some are even carcinogens. Most photodegradation initiators are composed of anthracene, phenanthrene, phenanthrene, benzophenone, alkylamine, anthraquinone and their derivatives. These compounds are all toxic substances and can cause cancer after prolonged exposure. These compounds produce free radicals under light, and free radicals will have adverse effects on the human body in terms of aging, pathogenic factors, etc. This is well known to all, and it causes great harm to the natural environment. In 1995, the US FDA (short for Food and Drug Administration) clearly stipulated that photodegradable plastics could not be used in food contact packaging.
2. Polypropylene: Polypropylene was gradually formed in the Chinese market after the original State Economic and Trade Commission issued the 6 order “prohibiting disposable foamed plastic tableware”. Because the former State Economic and Trade Commission banned “foamed plastics” and did not ban “non-foamed plastics” products, some people took advantage of the gaps in national policies. The toxicity of polypropylene has attracted the attention of the Student Nutrition Office of the Beijing Municipal Government. Beijing has begun to ban the use of polypropylene tableware among primary and middle school students.
3. Straw fiber packaging materials: As the color, sanitation, and energy consumption problems of grass fiber packaging materials are difficult to solve, the packaging materials standards issued by the former State Economic and Trade Commission and the State Technical Supervision Bureau in December 1999 included The color, hygiene, and heavy metals of packaging materials are the key inspection items, which limit the application of such materials in the market. Moreover, the strength problem of grass fiber packaging materials has not been solved, and it cannot be used as shock-proof packaging for household appliances and instruments, and the cost is relatively high.
4. Paper product packaging materials: Because paper product packaging materials require a large amount of pulp, and a large amount of wood pulp is added according to different requirements (such as instant noodle bowls need to add 85-100% of wood pulp to maintain the strength and firmness of the instant noodle bowl ),
Packaging Material Testing Center-Best Packaging and Transportation Testing Center is scientific and fair. In this way, the early-stage pollution of the pulp used in paper products is very serious, and the impact of wood pulp on natural resources is also considerable. Therefore, its application is limited. The United States used a large amount of paper packaging products in the 1980s and 1980s, but it has been basically replaced by starch-based biodegradable materials.
5. Fully biodegradable packaging materials: In the early 1990s, my country, together with developed countries such as the United States, Germany, Japan, and South Korea, successively carried out research on starch-based biodegradable packaging materials, and achieved gratifying results. As a naturally degradable material, biodegradable polymer has played a unique role in environmental protection, and its research and development have also been rapidly developed. The so-called biodegradable materials must be materials that can be completely digested by microorganisms and only produce natural by-products (carbon dioxide, methane, water, biomass, etc.).
As a disposable packaging material, starch has no pollution during production and use, and can be used as feed after use for feeding fish and other animals, and it can also be degraded as fertilizer. Among the many fully biodegradable packaging materials, polylactic acid (PLA), which is polymerized by biosynthetic lactic acid, has become the most active researcher in recent years due to its good performance and the application characteristics of both bioengineering materials and biomedical materials. biomaterials. Polylactic acid is a polymer obtained by artificial chemical synthesis of lactic acid produced by biological fermentation, but it still maintains good biocompatibility and biodegradability. Therefore, polylactic acid can be processed into various packaging materials, and the energy consumption of PLA production is only 20%-50% of that of traditional petrochemical products, and the carbon dioxide gas produced is only correspondingly 50%.
In the past 20 years, a new type of fully biodegradable packaging material-polyhydroxyalkanoate (PHA) has been rapidly developed. It is an intracellular polyester synthesized by many microorganisms and a natural polymer biomaterial. It has good biocompatibility, biodegradability and thermal processing properties of plastics, and can be used as biomedical materials and biodegradable packaging materials. This has become the most active research hotspot in the field of green packaging materials in recent years. But in terms of the current technical level, it is not appropriate to think that the use of these degradable materials can solve the “white pollution”, because the application performance of these products is not ideal, and there are still many problems. First of all, the price of biodegradable polymer materials is high and it is not easy to promote and apply. For example, the degradable polypropylene fast food box promoted on the railway in my country is 50% to 80% higher than the original polystyrene foam fast food box.
Secondly, the performance is not yet satisfactory. One of the main disadvantages of its use performance is that all starch-containing degradable plastics have poor water resistance, poor wet strength, and greatly reduced mechanical properties when exposed to water. Water resistance is precisely the advantage of current plastics during use. For example, the light-biodegradable polypropylene fast food box is less practical than the existing polystyrene foam fast food box, it is soft, and it is easy to deform when the hot food is installed. Styrofoam lunch boxes are 1~2 times larger. Polyvinyl alcohol-starch biodegradable plastic is used as a disposable cushioning material for packaging. Compared with ordinary polyvinyl alcohol cushioning materials, its apparent density is slightly higher, it is easy to shrink under high temperature and high humidity, and it is easy to dissolve in water. Water-soluble material.
Third, the problem of degradation control of degradable polymer materials needs to be solved. As a packaging material, it requires a certain period of use, and there is a considerable gap between accurate time control and complete and rapid degradation after use. There is still a considerable gap between practical requirements, especially for filled starch plastics, most of which cannot be degraded within one year. Although many experiments have proved that their molecular weight drops significantly under the action of ultraviolet rays, this is not the same as practical requirements. In developed countries such as the United States and Europe, they have not been accepted by environmental organizations and the public. Fourth, the evaluation method of biodegradability of polymer materials needs to be improved. Due to the many factors restricting the degradation performance of degradable plastics, there are many differences in the geographical environment, climate, soil composition, and garbage disposal methods of various countries. Therefore, what is meant by degradation, whether the degradation time should be defined, and what is the degradation product, these issues have failed to reach a consensus. The evaluation methods and standards are even more diverse. It takes time to establish a unified and complete evaluation method. Fifth, the use of degradable polymer materials will affect the recycling of polymer materials, and it is necessary to establish corresponding basic processing facilities for the used biodegradable materials. Although the degradable plastic packaging materials currently developed have not completely solved the increasingly serious “white pollution” problem, it is still an effective way to alleviate the contradiction. Its appearance not only expands the functions of plastics, but also eases the relationship between mankind and the environment, and promotes sustainable global development.
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