We all know that modern life is inseparable from takeaway. Most of the take-aways, whether they are bags or lunch boxes, are made of plastic. When we take out the take-away, after tearing away the exquisite packaging, we put them in a plastic bag with a lot of laziness, and then put those plastic boxes, plastic bowls, disposable chopsticks, plastic straws... together with leftovers. Throw it in the trash can downstairs in the community. Is this a problem? Maybe not. But many of us may not know that a plastic bag may last only a few hours, but how long does it last? 450 years. It takes 450 years to be degraded. Where did they go in the 450 years? According to an environmental organization survey, each single takeaway consumes 3.27 disposable plastic lunch boxes/cups, which means that the takeaway consumes more than 60 million lunch boxes per day. And the plastic waste generated by the takeaway is less than one thousandth of the total.
But what if we can improve this material for plastics?
So there is it-----environmental degradable material, which generally refers to a kind of material that can be naturally absorbed, digested and decomposed by the environment without generating solid waste.
So far, degradation can be achieved based on fully biodegradable plastics.
Biodegradable plastics are plastics that are degraded by the action of microorganisms (such as bacteria, fungi, and algae) that exist in nature. The ideal biodegradable plastic is a polymer material that has excellent performance, can be completely decomposed by environmental microorganisms after being discarded, and is finally inorganicized to become an integral part of the carbon cycle in nature.
Biodegradable plastics can be divided into two types: fully biodegradable plastics and biodestructive plastics (incompletely biodegradable plastics).
Completely biodegradable plastics are mainly made from natural polymers (such as starch, cellulose, chitin), microbial fermentation of agricultural by-products or synthetic biodegradable polymers. Such as thermoplastic starch plastics, aliphatic polyester, polylactic acid, starch / polyvinyl alcohol, etc. are all such plastics.
Destructive biodegradable plastics are mainly made by blending or copolymerizing natural polymer raw materials with general synthetic resins.
The degradation mechanism of biodegradation can be roughly divided into the following three stages of action:
The physical phase of the organism, causing mechanical damage to the plastic due to the growth of microorganisms;
In the biochemical stage, new substances are produced by the action of microorganisms on the polymer;
Direct action of the enzyme, microbial erosion leads to plastic splitting or oxidative cracking.
Factors affecting biodegradation:
The chemical structure of matter. The degree of difficulty in biodegrading organic matter depends first on the nature of the organism itself and on the structural characteristics of the organism.
Co-metabolism. Contaminants in the environment are often degraded by co-metabolism, especially for some complex organic pollutants.
Environmental physicochemical factors. Nutrients, aeration, pH, temperature, moisture, light and toxic substances required for microbial growth will affect the extent and speed of microbial degradation of pollutants.