Ordinary plastic is prone to white pollution and decomposes slowly in normal environments. Some people say that there are more plastics in the ocean than fish. It may be alarmist, but it makes us have to pay attention. With the continuous improvement of people's awareness of environmental protection, degradable plastics gradually to people's vision.
We Chinese value falling leaf to root, and we plastic people also hope that it can "fall leaf to root", after completing its mission, return to nature and become one with nature. As a result, degradable plastics came into being. Today, we talk about the seven most representative biodegradable plastics.
Polylactic acid PLA
Polylactic acid(PLA) is a new type of biodegradable material made from starch materials proposed by renewable plant resources such as corn. It has good biodegradability and can be completely degraded by microorganisms in nature after use. It eventually produces carbon dioxide and water and does not pollute the environment. This is very beneficial to the protection of the environment and is a recognized environmentally friendly material. It is understood that the PLA usage accounts for 45.1 % of biodegradable plastics, which is a well-deserved main force.
The degradation of polylactic acid is divided into two stages: 1) First, pure chemical hydrolysis into lactic acid monomer; 2) Lactic acid monomers degrade into carbon dioxide and water under the action of microorganisms. The food cup made of polylactic acid can be completely degraded in just 60 days, which really achieves ecological and economic effects.
PLA is mainly used for food packaging and 3D printing. The largest manufacturer of PLA is NatureWorks of the United States, followed by China's marine organisms.
Poly3-hydroxyalkane Ester PHA
PHA is an aliphatic copolymeric polyester synthesized by microorganisms from various carbon sources. The most common of these are poly3-hydroxybutyrate(PHB), polyhydroxypentate(PHV), and copolymers(PHBV) of PHB and PHV.
The main uses are: disposable tableware, non-woven cloth, packaging materials, agricultural film, toys, film, glue, fiber and other degradable products.
Domestic production of PHA companies include Tianjin Guoyun Biomaterials Co., Ltd., Wuhan Huali Technology Co., Ltd., Zhejiang Huafa Ecological Technology Co., Ltd., Zhejiang Tianhe Ecological Technology Co., Ltd., Fujian Zhaoqinghuafang Biomaterials Co., Ltd., and Tianjin Lifting Plastics Co., Ltd..
III. Polymer-hexolactone PCL
Polymer-hexolactone(PCL) is a low-melting point polymer obtained by ring-opening polymerization of hexolactone with a melting point of only 62 °C. The degradation of PCL has been studied since 1976. In anaerobic and aerobic environments, PCL can be completely decomposed by microorganisms.
Compared with PLA, PCL has better hydrophobicity but slow degradation rate; At the same time, the synthesis technology is simple and the cost is low. PCL has excellent processing performance and can be made of ordinary plastic processing equipment into thin films and other products.
PBS, which mainly produces aliphatic butyric acid and butanediol, can meet the demand not only through petrochemical products, but also through natural renewable crop products such as starch, cellulose, and glucose, and is produced by biological fermentation. In this way, we can realize the green cycle production from nature and return to nature. Moreover, the raw materials produced by biological fermentation process can also significantly reduce the raw material cost, thus further reducing the PBS cost.
Compared with similar products, polyester biodegradable plastic advantages:
1) Good heat resistance. This has led to its promotion in the catering field;
2) The processing conditions are not high;
3) Easy to preserve and resistant to hydrolysis.
Polybutanediol Ester(PBS) is widely used and can be used in packaging, tableware, cosmetic bottles and pharmaceutical bottles, disposable medical supplies, agricultural film, pesticide and fertilizer slow-release materials, biomedical polymer materials and other fields.
Aliphatic aromatic polyesters
The aliphatic aromatic polyesters(Ecoflex) manufactured by BASF, Germany, are monomers: adipic acid, terephthalic acid, and 1,4-butanediol. The current production capacity is 140,000 tons per year. At the same time, biodegradable plastic products based on polyester and starch were developed.
Water-soluble PVA film is a new plastic product that has emerged in the world. It uses PVA's membrane properties, water and biological degradation characteristics, and can be completely degraded to CO2 and H2O. It is a truly green, new and environmentally friendly packaging material.
In Europe, America and Japan, water-soluble PVA films have been widely used in the packaging of various products. In China, the development of water-soluble PVA films is still in its infancy, and industrial research and development has only really begun in the past five years. It is mainly used in the fields of embroidery and water transfer printing(color printing of glass, ceramics, electrical appliances, etc.). The annual use of PVA in this area is about 10000 T.
Carbon dioxide copolymers
A new type of synthetic material under research, using carbon dioxide as a monomer raw material, under the action of bimetallic coordination PBM Catalyst, is activated to a higher degree and copolymerized with epoxides to form aliphatic polycarbonate(PPC). After reprocessing, You get carbon dioxide resin.
In foreign countries, the first countries to study carbon dioxide copolymers were mainly Japan and the United States, but there has been no industrial production. Inner Mongolia Mengxi Group Co., Ltd. adopts the technology of the Changchun Institute of Applied Chemistry and has built a device with an annual output of 3,000 tons of carbon dioxide / cyclooxide copolymer resins. The products are mainly used in packaging and medical materials.