Urea-formaldehyde resin overview

Urea-formaldehyde resin

Urea-formaldehyde resins

The product name is Beetle. Also known as urea formaldehyde resin, referred to as UF, the average molecular weight is about 10,000. The urea and 37% aqueous formaldehyde solution can be polycondensed under the catalysis of acid or alkali to obtain linear urea powder urea-formaldehyde aldehyde oligomer. Industrially, the base is used as a catalyst, and the reaction is about 95 ° C, and the molar ratio of formaldehyde/urea is 1.5 to 2.0. To ensure that the resin can be cured. The first step of the reaction produces mono- and dimethylolurea, which is then further condensed with an amino group to give a soluble resin which, if catalyzed by an acid, tends to cause gelation. The product needs to be stored under neutral conditions. The linear urea-formaldehyde resin can be cured at room temperature when ammonium chloride is used as a curing agent. The molding powder is heat-cured at 130 to 160 ° C, and an accelerator such as zinc sulfate, trimethyl phosphate, diethyl oxalate or the like can accelerate the curing process. Urea-formaldehyde resins are mainly used in the manufacture of molded plastics, in the manufacture of household goods and electrical parts, as well as in sheet adhesives, paper and fabric pastes, veneers, architectural decorative panels, and the like. Due to its light color and easy coloration, the products are often rich in color and magnificence.

Urea-formaldehyde resin has low cost, light color, high hardness, oil resistance, mildew resistance, good insulation and temperature resistance, but poor weather resistance and water resistance. It is one of the earliest thermosetting resins developed. In 1924, the British cyanide company developed, the product was sold in 1928, the output in the mid-1930s reached 1,000 tons, and the world annual output in the 1980s exceeded 1.5Mt.

The amount of urea-formaldehyde resin used in the production of plastic products accounts for only about 10% of the total production. Urea-formaldehyde resin prepared in the case where the molar ratio of formaldehyde to urea is relatively low, and filler (pulp, wood powder), colorant, lubricant, curing agent, stabilizer (hexamethylenetetramine, ammonium carbonate), The plasticizer (urea or thiourea) and other components are mixed, and then dried, pulverized, ball milled, and sieved to obtain a urea-formaldehyde compression-molded powder. The temperature of the pressed urea-formaldehyde plastic is 140-150 ° C, the pressure is 25-35 MPa, and the pressing time varies depending on the thickness of the product, and is generally 10 to 60 minutes. Plastic products are mainly electrical lighting equipment and telephone parts.

Urea-formaldehyde resin is generally water-soluble resin, which is easy to cure. The cured resin is non-toxic, colorless, and light-resistant. It does not change color after long-term use, and does not change color during thermoforming. Various colorants can be added to prepare various bright colors. Products.

Urea-formaldehyde resin is hard, scratch-resistant, resistant to weak acid, weak alkali and oil, etc. It is cheap and has certain toughness, but it is easy to absorb water, and thus has poor water resistance and electrical properties, and is not high in heat resistance.