On Green Packaging Materials

Packaging not only makes the goods easy to transport and carry, but also protects and beautifies the goods, and plays a role in extending shelf life and promoting sales. With the continuous improvement of living standards, people have higher and higher requirements for the packaging of goods, leading to the rapid development of the packaging industry. However, while packaging brings convenience to people, it also poses a serious threat to the environment in which human beings live. On the one hand, packaging consumes a lot of resources and energy. On the other hand, packaging waste that has become more beneficial has become human. Second only to the fourth largest source of water pollution, marine lake pollution and air pollution.

When the contradiction between packaging and the environment is intensified, people propose the concept of developing “green packaging”. The so-called “green packaging” refers to the fact that the processing and production of raw materials and products have no pollution to the environment, can be recycled, recycled, or recycled. Nature's self-defense packaging. "Green packaging" is the most inspiring packaging revolution of the 21st century, an important part of the green wave.

To widely use green packaging and develop green packaging, people need to choose the right packaging materials. Therefore, green packaging is essentially green packaging materials. The so-called green packaging material (green packaging material) means that it can save resources and energy in the process of production, use, scrap and recycling, and can be rapidly and naturally degraded or reused after being discarded, without destroying the ecological balance, and it has a wide range of sources. , Materials or materials products with low energy consumption, easy recycling, and high recycling recycling rate.

At present, common green packaging materials are generally degradable plastics and natural biomolecular materials.

Degradable plastic

Plastic packaging material has brought great influence to modern civilization with its excellent performance. It has developed rapidly and has penetrated into various fields of industry, agriculture, national defense and daily life, bringing great convenience to people's lives. Its wide application has brought a "white revolution" to mankind. At present, the world's annual output of plastics has exceeded 200 million tons, of which 30% is used for packaging. However, since plastic packaging materials are mostly disposable consumer products, they are discarded after use, so that a large amount of waste is discarded in the environment, and because it is naturally degraded for a period of 200-300 years, it accumulates, and it seriously pollutes the living environment of human beings. The "white pollution" that people can hardly avoid has become a worldwide public hazard.

After entering the 1990s, although plastic packaging materials have always been seriously challenged by environmental problems, from the data published in recent years, at the beginning of this century, plastic packaging materials have become the fastest growing demand for materials in the packaging industry. One is still full of vitality. Therefore, we can neither stop the production of plastic packaging materials or discard them because we waste our food, but we cannot ignore them and ignore their environmental pollution. The objective situation requires that we must use a positive attitude and use the methods of developing science and technology and productivity to resolve this contradiction. Based on this, biodegradable plastic materials came into being.

Degradable plastics are considered to be the most promising green packaging materials, and are a new type of plastic that can quickly degrade and disappear in the natural environment after being discarded, and do not cause environmental pollution. China began to study blending from the early 1980s. Degradable plastics.

Degradable plastics can be divided into three types according to their degradation mechanisms: photodegradable plastics, biodegradable plastics, and biodegradable plastics.

1.1 Photodegradable plastic

Photodegradable plastics are materials that can be decomposed in an orderly manner under the irradiation of ultraviolet light. Photodegradable plastics based on cellulosic materials have been extensively studied at home and abroad. The basic method is to introduce a photosensitive group into the main chain, or add a photosensitizing chemical, a transition complex, and the like to the polymer. Under the irradiation of ultraviolet light, cellulose breaks down and generates pollution-free chemical substances such as xylose, xylobiose, glucose, disaccharide, acetaldehyde, acetic acid, carbon dioxide, water vapor, and the like.

1.2 Biodegradable plastics

Biodegradable plastics refer to plastic materials (including macromolecules and their complexes) that can be fully degraded into low-molecular compounds under the influence of various organisms in nature. Because it contains a certain amount of components that can degrade microorganisms and their enzymes, such as sugars, celluloses, organic acids, etc., it is an ideal plastic. Biodegradable plastics have roughly three types of degradation: biophysical effects, mechanical destruction of the polymer due to the growth of co-cells after microbial erosion, biochemical effects, and the action of microorganisms on polymers to produce new substances; direct enzymes As a result, microbiological erosion leads to plastic splitting or oxidation cracking.

Since most natural polymer materials have poor processing, thermal and mechanical properties, these molecules must be modified or blended to achieve their application value. In the field of packaging materials, composite materials based on starch, cellulose, etc. are more common.

1.2.1 Starch-Based Biodegradable Plastics

Starch-based fully biodegradable plastics are materials that are rapidly researching and developing, and have many industrialization results, and are expected to continue to reduce costs. In order to improve the compatibility of starch and polymer blends, it is necessary to modify the starch, and the surface of the modified starch granules is covered with an alkyl group, etc., which weakens the effect of hydrogen bonding, and with some synthetic resins such as polyethylene. The compatibility of polyvinyl alcohol, polyvinyl chloride, polyester, polystyrene and other polymers can be improved to varying degrees, and the properties of the blends are stronger than the original starch filling system. Due to the discontinuity of the plastic in the material, the starch in the plastic is gradually decomposed into small particles by microorganisms, thereby achieving the purpose of plastic degradation. However, the mechanical strength of such packaging materials is relatively small and cannot be used for more demanding applications, and?/td>

Various kinds of green plastic packaging materials

Corn plastic, an easily decomposable plastic, was developed in the United States. It was made by blending corn starch with polyethylene. The bag can be quickly dissolved in water, facilitate washing and cooking, and avoid the invasion of pollution sources and viruses.
British scientists from rapeseed plastics extracted three genes that can produce plastics from bacteria that make biopolymers, and then transferred them to rapeseed plants. After a period of time, they produced a plastic polymer liquid that was refined and processed. A canola plastic can be obtained. With this kind of plastic, it can be made into packaging materials or pediatric diapers, and can be dispelled by itself without any pollution residue.

Wood flour plastic This wood flour plastic was developed by Japan and was made from pine wood flour to remove polyols and then reacted with isocyanate to produce polyurethane. The plastic is extremely heat-resistant and biodegradable. It can be used to make heat-resistant bags.

Bacterial plastic This PHB bacterial plastic was developed in the United Kingdom. It uses sugar to grow a bacterium and then processes it into a similar material to polypropylene. The material is non-toxic and biodegradable. It is an ideal material for processing surgical sutures and food packaging bags.

Bioplastics Brazil has developed a new environmentally friendly substance called "biofoam" that can replace the current foam. 70% of the new substance is derived from corn, soy, and castor oil products, while petroleum extracts only account for 30%. Biofoam can be used as a lightweight packaging material that can be dissolved in nature in less than two years.

Source: China Packaging Industry