In recent years, with the rapid development of the economy, people's pursuit of material and spirituality has become higher and higher, and higher requirements have also been placed on the packaging of products. When people buy products, they not only look at the aesthetics of the outer packaging, but also consider Various other functions. It is precisely because of the continuous improvement of people's pursuit of product packaging that many new packaging materials have been continuously applied to the packaging of cup lid products.
Cup lid biodegradable materials, also known as "green ecological materials", refer to materials that can be degraded under the action of soil microorganisms and enzymes. Specifically, it refers to a polymer material that can be biodegraded under certain conditions under the action of natural microorganisms such as bacteria, molds, and algae. The ideal biodegradable material is a polymer material with excellent performance, which can be completely decomposed by environmental microorganisms after being discarded, and finally converted into CO2 and H2O to become an integral part of the carbon cycle in nature.
The decomposition of materials of biodegradable coffee lids is mainly through the action of microorganisms. Therefore, the degradation mechanism of biodegradable materials is the process of digestion and absorption of materials by bacteria, molds, etc. First, the microorganisms secrete hydrolase in vitro to combine with the surface of the material, and then the polymer chains on the surface are cut off by hydrolysis to generate compounds of small molecular weight, and then the degraded products are taken into the body by the microorganisms, and through various metabolic routes, the microorganisms are synthesized or transformed into microorganisms. The energy of the activity is eventually converted into water and carbon dioxide. According to the chemical nature of its degradation, it can be divided into two types: hydrolysis and enzymatic hydrolysis.
The degradation of the lid material is essentially a process in which the polymer segments inside are broken into low-molecular-weight oligomers under specific conditions, and finally decomposed into monomers. The "corrosion" of the material refers to the process in which the water-soluble small molecular substances formed leave the polymer material due to the breakage of the molecular chain, resulting in the reduction of the mechanical properties of the material and the final complete disappearance of the material.
If the degradation rate of the molecular segment is faster than the diffusion rate of water molecules in the material, the hydrolysis of the segment is limited to the surface of the material, and it is difficult to enter the interior of the material. This method belongs to surface dissolution or heterogeneous dissolution. If water molecules When the diffusion rate of the material is faster than the hydrolysis rate of the polymer segment, the degradation of the surface and the interior of the biodegradable coffee lid material is carried out at the same time, so it belongs to the overall corrosion.
Enzymatic hydrolysis mechanism
1. Enzymatic hydrolysis mechanism
For easily hydrolyzed polymers, there may be both simple hydrolysis and enzymatic hydrolysis in vivo. Lipase can promote the decomposition of polyester, and hydrolase can promote the degradation of easily hydrolyzable polymers. Lipase is the specific degrading enzyme of PCL. In the presence of these enzymes, the degradation rate of PCL is accelerated. It takes 2-3 years for complete degradation under normal circumstances, but the complete degradation time is shortened to a few days in the presence of enzymes.
2. Enzymatic oxidation mechanism
For some non-hydrolyzable polymers, the possible degradation mechanism is an enzymatic oxidation mechanism. Immunohistological studies confirmed that the lid material was finally absorbed and metabolized by phagocytic cell endocytosis in vivo. After the polymer biomaterial is implanted into the body, it will cause different degrees of acute inflammation in the local area. When the tissue is damaged, the permeability of the surrounding blood vessels changes, the multinucleated leukocytes move rapidly to the inflammatory site, and the activated neutrophils Can differentiate monocytes into macrophages. Metabolism by polymorphonuclear leukocytes and macrophages produces large amounts of peroxyanions, and this unstable intermediate is converted into the more potent oxidant hydrogen peroxide. The reduced coenzyme and oxidase in the body are involved in this conversion reaction, while superoxide dismutase plays a role in accelerating the conversion. Hydrogen peroxide may trigger the self-decomposition reaction of the polymer at the implantation site; meanwhile, hydrogen peroxide can be further converted into hypochlorous acid under the action of myoperoxidase. Hypochlorous acid is also a strong oxidant of biological materials, which can oxidize the amino groups in polyamide, polyurea, and polyurethane, and break the polymer chain, so as to achieve the effect of degradation.