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my country's current production and use of polymer materials have leapt to the forefront of the world, generating millions of tons of waste every year. So many polymers urgently need to be biodegradable to minimize pollution to humans and the environment. Biodegradable materials refer to materials that can be completely degraded into low-molecular-weight materials under the action of natural microorganisms, such as bacteria, molds and algae. This kind of material is convenient to store, as long as it is kept dry and does not need to be protected from light, it has a wide range of applications and can be used in fields such as mulching film, packaging bags, and medicine.
  The mechanism of biodegradability is roughly in the following three ways: biological cell growth causes mechanical destruction of substances; microorganisms produce new substances on polymers; the direct action of enzymes, that is, microorganisms attack polymers and cause lysis.
  According to the above mechanism, several main biodegradable polymer materials currently studied are introduced as follows.
  1. Concept and degradation mechanism of biodegradable polymer materials
  Biodegradable polymer materials refer to polymer materials that can be degraded by microorganisms or their secretions under enzymatic or chemical decomposition in a certain time and under certain conditions.
  The mechanism of biodegradability can be roughly divided into the following three ways: the growth of biological cells causes mechanical destruction of substances; the action of microorganisms on polymers produces new substances; the direct action of enzymes, that is, microorganisms attack polymers and cause lysis.
  It is generally believed that the biodegradability of polymer materials is carried out through two processes. First, the microorganisms secrete hydrolase in vitro to bind to the surface of the material, and cut the polymer chain through hydrolysis to generate small molecular weight compounds with a molecular weight of less than 500; then, the degraded products are taken into the human body by the microorganisms, and they are synthesized through various metabolic routes. The energy that is microbial or converted into microbial activities is ultimately converted into water and carbon dioxide.
  2, the type of biodegradable polymer material
  According to source, biodegradable polymer materials can be divided into two categories: natural polymer and synthetic polymer. Classified by use, there are two major categories of medical and non-medical biodegradable polymer materials. According to the synthesis method, it can be divided into the following types.
  2.1 Natural polymer type
Cellulose, chitin and lignin that exist in nature are all degradable natural polymers. These polymers can be completely degraded by microorganisms. However, due to the lack of physical properties of cellulose, the films made from them are Water resistance and strength are not up to the requirements. Therefore, it is mostly made by blending with other polymers, such as deacetyl polysaccharides made from chitin. 2.4 Blending type In the non-biodegradable polymer material, a certain amount of biodegradable polymer compound is blended, so that the resulting product has a considerable degree of biodegradability, which makes a blended biodegradable polymer material. Degradable polymer materials, but this material cannot be completely biodegradable.
  2.2 Microbial production type
  High molecular substances synthesized by microorganisms. Such polymers mainly include microbial polyesters and microbial polysaccharides, which are biodegradable and can be used to produce biodegradable plastics that do not pollute the environment. Such as the "Biopol" product produced by the British ICI Company.
  2.3 Synthetic polymer type
  Aliphatic polyester has good biodegradability. But its low melting point, poor strength and heat resistance, cannot be used. Aromatic polyesters (PET) and polyamides have high melting points and good strength. They are engineering plastics with high application value, but they are not biodegradable. The aliphatic and aromatic polyester (or polyamide) is made into a copolymer with a certain structure. This copolymer has good properties and a certain degree of biodegradability.
  3. Application of biodegradable polymer materials
  Currently, biodegradable polymer materials are mainly used in two aspects: (1) Using their biodegradability to solve environmental pollution problems to ensure the sustainable development of the human living environment. Generally, there are three main methods for processing polymer materials: landfill, incineration, and recycling, but these methods have their drawbacks. (2) Use its degradability to be used as a biomedical material. At present, my country produces more than 300 billion tablets and controlled-release capsules a year, of which more than 70% are coated epidermis, and more than 80% of the coated tablets are traditional sugar-coated tablets. More than 80% of the country uses water-soluble polymer materials as film-coated tablets. Therefore, there is a big gap between my country's tablet manufacturing level and the international advanced level. Foreign tablets and film-coated tablets mostly use hydroxypropyl methylcellulose, hydroxypropyl cellulose, acrylic resin, polyvinylpyrrolidone, cellulose acetate, cellulose acetate phthalate, sodium hydroxymethyl cellulose, microcrystalline fiber Vegetarian, sodium hydroxymethyl starch, etc.
  With the birth of biodegradable polymer materials, our living environment is slowly being optimized. I believe that in the near future, we will be able to have a beautiful home again!