Degradable plastic science knowledge series(一)

Degradable plastic science knowledge series(一)

Time:2022-2-19

What is degradable plastic?

Degradable Plastics Committee: Degradable plastics is a big concept, which is the loss of certain properties (such as integrity, integrity, molecular mass, structural or mechanical strength) and/or plastics that have broken down. Among them, photodegradable plastics and thermo-oxidatively degradable plastics are broken plastics and should not be attributed to biodegradable plastics. Degradable plastics should be tested using standard test methods that reflect changes in properties, and should be classified according to the manner of degradation and life cycle. Without combining the types of degradable plastics and their degradation environmental conditions, and generally speaking of degradable plastics, it does not mean that such plastics can be completely degraded into substances that are harmless to the environment.

Degradable plastic science knowledge series(一)
Degradable plastic science knowledge series(一)

Special Committee on Degradable Plastics: 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 plastics refer to the degradation caused by the action of microorganisms existing in nature under natural conditions such as soil and/or sandy soil, and/or specific conditions such as composting conditions or anaerobic digestion conditions or aqueous culture solutions, and The final complete degradation becomes carbon dioxide (CO2) or/and methane (CH4), water (H2O) and mineralized inorganic salts of the elements it contains, and new biomass (such as dead microorganisms, etc.).

It should be noted that each biodegradable material, including paper, etc., requires certain environmental conditions for its degradation. If there are no degradation conditions, especially microbial living conditions, the degradation will be very slow; at the same time, not every Biodegradable materials degrade rapidly under any environmental conditions. Therefore, when dealing with biodegradable materials, we should proceed from its environmental conditions and analyze the material itself to determine whether it is a biodegradable material. How to judge whether a material is biodegradable? Both the world and China have issued a series of test method standards, which are answered in the standard question.

Degradable plastic science knowledge series(一)

What types of biodegradable plastics are there?

Special Committee on Degradable Plastics: According to the source of raw materials of biodegradable plastics, it can be divided into two categories: bio-based biodegradable plastics and petrochemical-based biodegradable plastics.

Bio-based biodegradable plastics can be mainly divided into four categories:

The first category is plastics directly processed from natural materials. Currently, biodegradable plastics produced from natural polymers on the market mainly include thermoplastic starch, biocellulose, polysaccharides and polyamino acids, as well as their blending modification and chemical modification. product of sex;
The second category is polymers obtained by microbial fermentation and chemical synthesis, such as polylactic acid (PLA);
The third category is polymers directly synthesized by microorganisms, such as polyhydroxyalkanoates (PHA), etc.;
The fourth category is the biodegradable plastics obtained by blending the above materials or by 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.

What are compostable biodegradable plastics?

Degradable Plastics Committee: Composting is an aerobic treatment method to produce compost. Compostable refers to the ability of materials to be biodegraded during the composting process. A material including paper, plastic, etc., if claimed to be compostable, it must be stated that the material is biodegradable and disintegrates in the composting system (as shown in standard test methods) and is fully biodegradable in the compost end use . Compost must meet relevant quality standards. Quality criteria such as low heavy metal content, no biological toxicity, no clearly distinguishable residues.

Degradable plastic science knowledge series(一)

What is the difference between industrial composting and home composting?

Special Committee on Degradable Plastics: Fertilizer is an organic soil conditioner obtained by the biological decomposition of the mixture. The mixture is mainly composed of plant residues, and sometimes also contains some organic material and some inorganic substances. The raw materials of composting can be urban and rural organic solid waste, such as agricultural crop straw, rural farming manure, urban domestic waste, kitchen waste, municipal sludge, food industry waste, etc. Composting, a treatment method that produces compost, is a biochemical process that uses microorganisms widely existing in nature to control the conversion of degradable organic matter in solid waste into stable humus. Composting can be divided into aerobic composting and anaerobic composting according to the process of microbial growth and whether oxygen is supplied. Aerobic composting is the process of decomposing organic matter in the presence of oxygen, and the final products are CO2, H2O, heat And humus, anaerobic composting is under anaerobic conditions, anaerobic microorganisms degrade organic matter into CH4, CO2, H2O, heat and humus. Composting is usually referred to as aerobic composting.

Industrial composting refers to the process of aerobic mesophilic or high-temperature degradation of solid and semi-solid organic matter by microorganisms under controlled conditions to produce stable humus. The general cycle is 180 days, but with changes in aerobic composting technology, the shortest time is 30 days or even shorter.

Home composting refers to the process of aerobic composting mainly using home kitchen waste or garden waste to produce compost for home use. Home composting takes longer than industrial composting, but generally no longer than a year.

Whether it is industrial composting or household composting, the organic wastes it processes should have the following characteristics:

a) biodegradability (i.e. the original biodegradability of the material);

b) disintegration properties during composting;

c) will not adversely affect the biodegradation process;

d) Adverse effects on final compost quality such as excess of harmful elements.

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