Degradable plastics are plastics that can be degraded. Under certain conditions, they can be completely transformed into carbon dioxide, water and other small molecular biomass, and will not remain in the environment to cause white pollution.
So why can degradable plastics degrade and what is its degradation principle?
Traditional plastics, such as polyethylene, the main component of plastic bags, are polymers of ethylene monomers, with high molecular weight and tight connection between molecular bonds, which are difficult for microorganisms to digest and absorb.Biodegradable plastics often contain heteroatoms that are more preferred by microorganisms such as N and O, which can be digested and absorbed by microorganisms quickly. In addition, biodegradable plastics mostly contain ester bond structures, which are prone to hydrolysis, which also accelerates the overall degradation rate of the plastic.
We can divide the degradation of biodegradable plastics into two processes:
1. The hydrolysis process of polymer chains into small molecule fragments
Under the various effects of microorganisms and the natural environment, the degradable plastic changes its physical form from a large plastic film to a small piece of plastic fragments, which is more conducive to the attachment of microorganisms. At the same time, the long-chain structure of degraded plastics becomes short-chain, which is easier for microorganisms to digest.
Changes in physical form can significantly accelerate the degradation rate of degradable plastics. If a scientist conducts an experiment on degrading enzymes in cattle stomachs, adding a whole piece of degradable plastic film and powdered plastic particles to the enzyme solution, and comparing them, it turns out that the degradation rate of degradable plastic in powder form is faster. The latest research: beef gastric juice is too good! Can degrade PET, PBAT and other plastics.
The seawater-degradable plastics currently under study are polycondensed into new polymers by adding glycolic acid and other easily hydrolyzable fragments to the molecular chain. Among them, the hydrolysis of easily hydrolyzed fragments can effectively accelerate the transformation process of degraded plastics from macromolecules to small molecules, and ultimately accelerate the overall degradation rate of plastics.
For the degradation of degradable plastics, the process of turning large films into small fragments and polymer chains into small molecular fragments is the decisive step in the overall degradation rate of degradable plastics. How to speed up the hydrolysis process is the key to improving the degradation rate of degradable plastics.
2. The degradation process of small molecules under the action of microorganisms
After being hydrolyzed, microorganisms can better "eat" these small plastic degrading molecules. Microbes secrete specific degrading enzymes. After digestion, small molecular fragments are absorbed by the microbes and converted into carbon dioxide, water, and biomass used to synthesize the microbes themselves.
At this time, the degradable plastic has completed its entire cycle in nature, from petroleum or plants to molecular monomers, and then polymerized from monomers into degradable plastics and processed into various plastic products. Finally, in the microbial environment Under the action, it transforms into water, carbon dioxide, and biomass, and returns to the natural environment in another harmless form.
