Urea formaldehyde

Due to the shortcomings of urea formaldehyde resin such as terrible preliminary viscosity, massive shrinkage, excessive brittleness, water resistance, handy aging, launch of formaldehyde, and air pollution of the surroundings and injury to fitness in the course of curing, it is integral to regulate it to enhance its overall performance and increase its application. The amendment techniques are quickly listed as follows:
1. Increase preliminary viscosity
To enhance the preliminary viscosity of urea formaldehyde resin, modifiers such as polyvinyl alcohol, polyethylene glycol, and hydroxymethyl cellulose can be added. However, these components are expensive, so starch primarily based materials can be selected, specially when starch is introduced at the opening of urea formaldehyde resin synthesis, which has a higher effect. In the system of synthesis, starch can also endure hydrolysis to produce more than a few dextrins. Due to the excessive molecular weight of starch and the excessive viscosity after dissolution, a small quantity of starch can be delivered to produce urea formaldehyde resin with excessive viscosity. At the equal time, hydroxyl groups, hydroxymethyl groups, and aldehyde corporations generated with the aid of hydrolysis on the starch molecular chain may also take part in the synthesis response of urea formaldehyde resin, which now not solely improves the preliminary viscosity, however also improves the bonding power and storage stability.

2. Reduce contractility
Urea formaldehyde resin has a excessive curing shrinkage fee and is susceptible to cracking, ensuing in inner stress in the adhesive layer and a reduce in viscosity and strength. In order to minimize the shrinkage charge of urea formaldehyde resin at some stage in solidification, some fillers such as flour, starch, blood powder, a-cellulose powder, timber powder, soybean powder, etc. are commonly introduced to the resin adhesive.
3. Reduce brittleness
In order to limit brittleness and enhance toughness, polyvinyl alcohol, polyvinyl formal solution, polyvinyl acetate lotion, VAE solution, etc. can be added, and the preliminary viscosity and growing old resistance can additionally be improved.
4. Improving water resistance
Adding a small quantity of melamine, phenol, resorcinol, alkylamine, sugar formaldehyde, etc. to the synthesis of urea formaldehyde resin can efficiently enhance its water resistance. Adding aluminum sulfate, aluminum phosphate, and different crosslinking dealers can additionally appreciably enhance water resistance. Adding fillers such as wooden flour, flour, soybean flour, iron oxide, and expansive soil all through glue mixing can additionally enhance water resistance.
Phenol modified urea formaldehyde resin is used, and a benzene ring shape is added into the resin to block the water absorbing team of the resin, notably enhancing its water resistance and getting older resistance. The water resistance can additionally be extended by way of including resorcinol or melamine into the curing agent components, and by way of mixing acrylate copolymerization lotion with urea formaldehyde resin.
5. Improve bonding strength
The use of a couple of composite components such as polyvinyl alcohol and phenol can enhance brittleness, water resistance, and adhesive strength. Then the compound manner of impartial vulnerable acid vulnerable base was once adopted, and the response used to be carried out at medium temperature. The shear electricity of the UF resin was once extra than 10 instances that of the authentic UF adhesive, and the water resistance and boiling resistance had been noticeably improved.