What are the commonly used modification methods for urea formaldehyde resin

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Regarding the commonly used modification methods for urea formaldehyde resin, the editor will provide a detailed introduction for everyone. Follow us to learn more.
Improve water resistance
Overview: The main factor affecting the water resistance of urea formaldehyde resin adhesive is the presence of some hydrophilic groups in the resin.
Solution: Add polyvinyl acetal, phenolic (PF) resin, melamine formaldehyde (MF) resin, epoxy resin and other hydrophobic resins with good bonding performance. Blending and modifying the resin to improve its water resistance. Compounds that can participate in the copolymerization of urea and formaldehyde use melamine, Resorcinol, aniline and furfural as raw materials to introduce hydrophobic groups into the resin through the copolymerization reaction. If some alcohols, such as butanol and furfuryl alcohol, are added in the later stage of resin synthesis to etherify the hydroxyl group, it can also improve the water resistance of the resin. If both physical co mixing and co condensation methods are used to modify the resin, the effect will be better.
Study on the Stability of Resins
The higher the degree of polymerization of the resin, the poorer its water solubility, and the shorter its storage period; The more amino and imino groups contained in Condensation polymer, the easier crosslinking will occur and the worse stability of the resin will be; During the storage process of the resin, the pH value of the system will gradually decrease, leading to early solidification. Therefore, by detecting and adjusting the pH value of the resin during storage, the storage performance of the resin can be extended. In addition, its storage stability is also related to the content of impurities in the raw materials.
Study on the Aging Resistance of Urea Formaldehyde Resin
Overview: Resin aging refers to the gradual occurrence of aging cracks and debonding in the cured adhesive layer.
Reason: There are many factors that affect resin aging, among which the main reason is that the resin still contains some free hydroxymethyl groups after curing. They are hydrophilic and further decompose to release formaldehyde, causing the adhesive layer to shrink.
To improve the brittleness of the resin, thermoplastic resins such as polyvinyl formal can be added to the resin.
In the process of resin synthesis, adding ethanol, butanol, furfuryl alcohol for hydroxymethyl etherification, or phenol condensation, melamine and urea can improve its anti-aging performance.
When mixing, add appropriate proportions of flour, wood flour, soybean flour, bentonite and other fillers. For urea formaldehyde resin, it can reduce the stress concentration caused by the volume shrinkage of the adhesive layer, leading to adhesive opening and detachment. In addition, magnesium oxide and Wood ash are used as acid removers to reduce the acid concentration in the adhesive layer, which can improve the aging resistance and water resistance.


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