The danger of moldy paint coating

2021-10-31   Pageview:521

After the moldy interior wall coating, it will lead to the rapid growth of Aspergillus niger and some molds, which will also lead to moldy or even blackened wall surface over time. Then even make the coating film off, bringing economic losses to manufacturers and users.











Photodegradation of polyurethane acrylate based on MDI
Aliphatic urethane acrylate coating can still maintain transparency and colorlessness after 2000h Q UV aging test, but infrared (IR) spectrum analysis clearly shows that it has undergone photodegradation reaction, and urethane bond units are found All important absorption bands (NH, NC, CH, CO, CO) gradually decrease after radiation. At the same time, due to photooxidation, the hydroxyl content in the coating increases, which is reflected in the hydroxyl group near 3280cm in the infrared spectrum. The absorption peak gradually increases. The intensity change of the infrared signal of the urethane bond is also often used as an important indicator to evaluate the photo-aging of the polyurethane coating.

Polyester system: When investigating the photo-aging behavior of polyester, it is also necessary to consider whether the polyester segment contains an aromatic ring structure. The possibility of aging and yellowing is greater.
In addition, polyester resins based on aromatic carboxylic acids can also undergo an sasol wax emulsion intramolecular hydrogen abstraction process.

Nor rihⅡ type photolysis occurs to generate aromatic acids and double bond structures. Substituted biphenyl structures and substituted phenolic structures are also possible photolysis products [24.251. The structure of aliphatic polyester mainly undergoes ester bond cleavage, forming acyloxy radicals and alkyl radicals, which are then attacked by oxygen molecules, which may eventually produce carbon dioxide (acyloxy radicals decarbonylation), peroxides, alcohols, carboxylic acids, etc. Degrading the structure, the intermediate free radicals may undergo grafting, coupling, and crosslinking reactions at the same time. In the aliphatic polyester acrylate cross-linking system, the hydrogen abstraction process between the ester carbonyl group and βH is more common, which eventually leads to the cleavage of the molecular chain and the basic process of photolysis.


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