Alkyd resin is a type of synthetic resin derived from the polycondensation of polyols (like glycerol), dibasic acids (such as phthalic anhydride), and fatty acids or oils. It is widely used as a binder in coatings, varnishes, and paints due to its excellent adhesion, gloss, and durability.

Alkyd resins are known for their versatility and can be modified to suit different applications. They are commonly used in architectural coatings, industrial finishes, and even in some automotive paints. The drying process of alkyd-based coatings involves oxidation, which allows them to form a hard, durable film over time. This makes them particularly suitable for protective and decorative finishes on wood, metal, and other materials.

Cellulose fibers are hydrophilic; when paper is soaked in water, the fibers swell, the bonding forces between them weaken, and the paper loses most of its strength, with the remaining strength often referred to as wet strength. Generally, paper with wet strength greater than 15% is considered wet strong paper. Since urea-formaldehyde resin is non-ionic, it cannot be well absorbed by paper fibers with negative charges; therefore, it cannot be added directly to the pulp when used as a paper wet strength agent and can only be applied using impregnation methods (such as surface coating).

Urea-formaldehyde resin, as a paper wet strength agent, forms a networked structure around the fibers through chemical crosslinking, which is not susceptible to hydrolysis. This prevents the absorbent swelling of the hemicellulose in the paper, reducing the paper’s strength loss under wet conditions, much like a net that constrains the swelling of the fibers, thereby maintaining the paper’s wet strength.

Traditional urea-formaldehyde (UF) resin has been banned abroad due to the hazard of free formaldehyde. However, formaldehyde-free wet strength agents are more expensive, leading to research into modified urea-formaldehyde resins. Synthesizing urea-formaldehyde resin using glyoxal partially or entirely replacing formaldehyde, and the effects of the resulting product on paper wet strength, shows that the product is non-polluting, has good stability, and significantly enhances strength.