What is degradable plastic? Degradable plastic knowledge answer
1. What is a biodegradable material?
A: Biodegradable materials include biodegradable natural polymer materials such as cellulose, starch, paper, etc., as well as biodegradable plastics obtained by biosynthesis or chemical synthesis.
Biodegradable plastic refers to degradation caused by the action of microorganisms existing in nature under natural conditions such as soil and/or sand, and/or specific conditions such as composting conditions or anaerobic digestion conditions or in aqueous culture fluids. Eventually, it will completely degrade into carbon dioxide (CO2) or/and methane (CH4), water (H2O) and mineralized inorganic salts of the elements contained therein, as well as new biomass (such as microbial dead bodies, etc.).
It should be noted that every biodegradable material, including paper, requires certain environmental conditions for its degradation. If it does not have the degradation conditions, especially the living conditions of microorganisms, its degradation will be very slow; at the same time, not every kind of organism Degradable materials can quickly degrade under any environmental conditions. Therefore, when dealing with biodegradable materials, we should start from its environmental conditions and analyze the structure of the material itself to determine whether it is a biodegradable material. How to judge whether a material is biodegradable, both the international and China have issued a series of testing method standards, which are answered in the standard question.
2. What types of biodegradable plastics are there?
A: According to the raw material source of biodegradable plastics, it can be divided into bio-based biodegradable plastics and petrochemical-based biodegradable plastics.
Bio-based biodegradable plastics can be divided into four categories: The first category is plastics directly processed from natural materials. At present, biodegradable plastics produced by natural polymers on the market mainly include thermoplastic starch, biocellulose, and polysaccharides. And polyamino acids and their blending modification and chemical modification products; the second category is the polymer obtained by microbial fermentation and chemical synthesis, such as polylactic acid (PLA), etc.; the third category is the polymerization directly synthesized by microorganisms Materials, such as polyhydroxyalkanoates (PHA), etc.; the fourth category is biodegradable plastics obtained by blending these materials or blending these materials with other chemically synthesized biodegradable plastics.
Petrochemical-based biodegradable plastics refer to plastics obtained by polymerizing petrochemical monomers by chemical synthesis, such as polybutylene terephthalate adipate (PBAT), polybutylene succinate (PBS) ), carbon dioxide copolymer (PPC), polyglycolic acid (PGA), etc.
3. Will the large-scale production of biodegradable plastics cause a food crisis?
A: At present, the global production capacity of biodegradable plastics is about 1 million tons, with an annual growth rate of about 20% to 30%. At present, it is mainly fossil-based PBAT and other biodegradable plastics. Among these plastics, the biodegradable plastics prepared from corn starch as raw materials are mainly polylactic acid. The current global production capacity of polylactic acid is about 280,000 tons/year, and the apparent consumption is about 160,000 tons/year. Even if the polylactic acid production capacity construction in some reports has been achieved in recent years, the biodegradable plastics prepared from corn starch as raw materials are only about one million tons, which will not have a fundamental impact on food. From the past five years or longer, the development of biodegradable plastics has had a very low impact on the food crisis.