Polyvinyl alcohol (PVA) is an important polymer material. Due to its good physical properties and chemical stability, it is widely used in textile, papermaking, construction, glue and other fields. It is of great significance to study the degradation mechanism and products of PVA.
Degradation mechanism of PVA:
1. Photocatalytic degradation
Photocatalysis refers to the process of using electrons generated on the surface of semiconductor materials to perform chemical reactions under the action of light. PVA can be decomposed into low molecular weight products under the action of photocatalysts.
2. Thermal degradation
Thermal degradation refers to the decomposition of polymer materials into low molecular weight products due to chain breakage and oxidation reactions under high temperature conditions. PVA can undergo reaction steps such as cracking, dehydration and oxidation under high temperature conditions.
3.Biodegradation
Biodegradation refers to the conversion of polymer materials into low molecular weight products through metabolic processes in organisms such as microorganisms or enzymes. PVA can be broken down into low molecular weight products through microbial metabolism.
Main degradation products of PVA:
1.Ethanol
Ethanol is one of the main products of thermal degradation of PVA. It is generated due to the reaction between the hydroxyl group and the aldehyde group formed by the cleavage of the ester bond within the PVA molecule to generate alcohols.
2.Formaldehyde
Formaldehyde is also one of the main products of thermal degradation of PVA. It is generated due to the reaction of the hydroxyl group formed by the cleavage of the ester bond within the PVA molecule and the aldehyde group to form ethyl formate, which is then decarboxylated to form formaldehyde.
3.Ethylene
Ethylene is one of the products of photocatalytic and thermal degradation of PVA. In photocatalytic degradation, PVA will undergo chain scission after being exposed to ultraviolet light, forming hydrocarbon free radicals, and then an addition reaction will occur to generate ethylene. In thermal degradation, chain scission and dehydration reactions occur within PVA molecules under high temperature conditions, ultimately generating ethylene.
4.Carbon dioxide
Carbon dioxide is one of the main products produced during biodegradation. During microbial metabolism, PVA is converted into low molecular weight products such as carbon dioxide and water.
5. Acetic acid
Acetic acid is one of the main products produced during biodegradation. During microbial metabolism, PVA is converted into low molecular weight products such as acetic acid and water.
By studying the degradation mechanism and main degradation products of PVA, we can provide a theoretical basis for improving the environmental friendliness of PVA. At the same time, it can also provide reference for the research of polymer materials.
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