As an important basic material, plastics are widely used in social production and residents' lives. Non-standard production, use and disposal of plastics will cause waste of resources and energy, bring ecological environmental pollution, and even affect the health and safety of the masses.
According to the United Nations Environment Programme, humans produce more than 400 million tons of plastic every year, and about 10 million tons of plastic waste ends up in the ocean every year. According to the Communique on the State of China's Ecological Environment in 2022, among the floating garbage at sea, beach garbage, and submarine garbage, the amount of plastic garbage is the largest, accounting for more than 80%, mainly foam, plastic rope, plastic debris, and plastic bottles.
Plastic waste pollution control is urgent, reducing the amount of plastic waste generation, recycling and reuse of plastic waste, plastic waste into the controllable scope of effective human management is a reference treatment.
Therefore, degradable materials into people's vision, of which PLA and PBAT are the most common, no more details, today we introduce a natural polymer degradable material - PHA.
Basic situation
polyhydroxyalkanoates (PHA), which are aliphatic copolyesters with different structures synthesized by microorganisms through various carbon sources, are a kind of natural macromolecular biomaterials. Because PHA has good biocompatibility, biodegradability and thermal processing properties of plastics at the same time, it can be used as biomedical materials and biodegradable packaging materials, so it has become the most active research hotspot in the field of biological materials in recent years. PHA also has nonlinear optical property, piezoelectric property, gas separation and many high value-added properties.
Product characteristics
As a natural polymer material, PHA certainly has the basic characteristics of common polymers, such as thermal plasticity or thermal processability. At the same time, PHA also has some special material characteristics, such as nonlinear optical activity, piezoelectric property, gas barrier property, and its basic properties are similar to polypropylene.
Compared with PLA and other biological materials, PHA structure is diversified, and the composition of PHA can be easily changed by changing the strain, feed and fermentation process, and the diversification of properties brought by the diversity of composition structure makes it have obvious advantages in application. According to the composition of PHA, it can be divided into two categories: one is short-chain PHA(monomer C3-C5), and the other is medium-long chain PHA(monomer C6-C14). It has been reported in recent years that strains can synthesize short-chain and medium-long chain copolymerized hydroxyl fatty acid esters. The production of PHA has experienced the production of the first generation of PHA - polyhydroxybutyrate (PHB), the second generation of PHA - hydroxybutyrate copolyester (PHBV) and the third generation of PHA - hydroxybutyrate copolyester (PGBHHx), and the PHBHHx of the third generation of PHA is the first large-scale production by Tsinghua University and its cooperative enterprises. The fourth generation product P34HB (poly3-hydroxybutyrate / 4-hydroxybutyrate copolymer), the domestic production enterprises are mainly Tianjin Guoyun Biological Materials Co., LTD. (10,000 tons/year) and Shenzhen Yikeman Biotechnology Co., LTD. (5,000 tons/year). [3] Compared with the production process of traditional chemical plastic products, the production of PHA is a production with low energy consumption and low carbon dioxide emissions, so it is very beneficial to environmental protection from the production process to the product.
Due to its complete non-toxic side effects, the recycling and disposal of PHA is also unique, and it can be recycled as animal feed. Traditional waste plastics are generally disposed of by landfill or incineration, resulting in land, air and other pollution problems. And PHA can be processed after some series of processing, as a feed can produce economic benefits again, to achieve the double cycle of material and economy.
In addition, PHA is also a very good solution to the problem of plastic abandonment in the sea. In the ocean, PHA will be degraded into microplastics, which are eaten by native animals such as paramecium in the water body, and some small fish and shrimp can also be eaten, so that the problem of plastic abandonment in the sea can be fundamentally solved.
In addition to the product itself is completely green and non-toxic, PHA raw materials also have the characteristics of low carbon and sustainable development, in the context of China's "double carbon" strategy, the whole process of low carbon is of vital significance. PHA raw materials are starch, straw hydrolysate, etc. These raw materials are green plants that consume carbon dioxide in their growth process, and their manufacturing process only needs room temperature and pressure, compared with other production processes that require high temperature and high pressure energy consumption materials, room temperature and pressure itself is a kind of carbon reduction. At the same time, in terms of industrial safety, compared with high temperature and high pressure explosive petroleum-based products, the PHA water-based production process at normal temperature and pressure is milder and does not produce safety risks.
PHA is not only an environmentally friendly bioplastic with excellent performance, but also has many adjustable material properties, and with the further reduction of cost and the development of high value-added applications, it will become a cost can be accepted by the market in multi-application fields of biological materials. Because it is a widely composed family, its properties from hard to highly elastic make it suitable for different application needs. The diversity of PHA structures and the variability of its properties make it an important member of biomaterials. Compared with PLA, PHA has a short history of development, greater potential for development, and greater space for its application.
Blending advantage
PHA is a general term for a large class of materials, and there are many subdivided materials with different properties. Overall, the relationship between PHA and petroleum-based degradable plastics is complementary rather than competitive. The degradation rate of PBS and PLA in the natural environment can be controlled by blending with PHA materials, and if buried in the soil, it can be completely degraded in a short time.
Compared with traditional plastics, various degradable plastics can also be improved in hardness, elasticity and other material properties by blending with various complementary properties of PHA. For example, for the low hardness of PBAT, rigid PHA can be added to increase the hardness; For the problem of low elasticity of PBAT, high-elastic PHA can be added to improve the performance, and the same is true for materials such as PBS. PLA is relatively rigid and heat-resistant, and PHA blends with complementary properties can be used to improve the application capability. For example, the current degradable plastic bags are generally soft material problems, can be blended with PHA to improve the performance, so as to expand the application scenario of PLA.
In summary, PHA and existing biodegradable materials are complementary advantages, with a large number of degradable plastics such as PBAT, PBS and PLA on the production capacity, based on the advantages of blending, the production capacity of PHA will also be driven.
At present, PBAT, PBS, PLA and other materials have a relatively mature production process, while PHA is still under development, in the future, PHA is likely to become a more easily recognized by the market in the biological field of materials, as one of the main development directions of degradable materials.
