Urea formaldehyde resin Molding compound

Candelilla (Euphorbia cerifera) wax Melamine-formaldehyde resin Methyl methacrylate Novolac resin Silicone Urea-formaldehyde resin molding compounds, amorphous boil-in-bag pouches... 

Molding Powders. Urea-formaldehyde resins are compounded with alpha-cellulose cotton fiber reinforcement to produce molding powders (4 percent) for compression, transfer, and injection molding. Typical molding conditions are 127 to 182°C and 2000 to 8000 psi. They are superior to phenolics in white color, electrical resistance, and low cost, but are limited by moisture sensitivity (Table 3.13). They are used primarily in electrical wiring devices such as wall outlets, receptacles, electric blanket controls, circuit breakers, and knob handles. Smaller amounts are used in bottle caps, housewares, buttons, and sanitary ware. 

Fillers in Thermosets. Sixty-five years ago, in a paper presented before the American Chemical Society, L. H. Baekeland (55) discussed the usefulness of phenol-formaldehyde resins that, when compounded with wood flour, could be molded. Wood flour, ground nut shells, a-cellulose, or paper add bulk to phenolics, melamine, or urea-formaldehyde resins and make them easier to fabricate and less expensive. 

Note As this table shows, the largest outlet for amino resins by far is their use as adhesives or binders for reconstituted wood products made from sawdust and wood chips. Urea-formaldehyde resin is most commonly used. Melamine-formaldehyde resin can provide improved water resistance and may be combined with the urea resin to provide an improved product. Molding compounds are about the next most important outlet for amino resins. It is approximately evenly divided between urea and melamine. The primary use for urea moldings is in the electrical field, while the most important area for molded melamine plastic is dinnerware. 

Thus, urea formaldehyde resins are particularly suitable as rapid-setting (curing, hardening) molding materials. Aniline formaldehyde resins are hardened with compounds such as paraformaldehyde, hexamethylene tetramine, or furfurol, since as no polycondensation reactions occur in the absence of acid catalysts, pre-cross-linked products have to be used for this purpose. Aniline resins therefore cannot be used as rapid-setting molding materials (cf. Section 12.2.2). 

Although the chemistry of the reaction of formaldehyde with urea and other amino compounds was investigated much earlier, the first useful product did not come on the market until the 1920s. The first commercial application for amino resins was in molding compounds and utilized a resin made with an equimolar combination of urea and thiourea, the invention of Edmond C. Rossiter ( ). The Beetle brand name was applied to the new molding compound and has remained prominent in amino resins ever since. It is of special interest that the very first commercial product based on amino resins should be a complex formulation such as a molding compound. 

Melamines. Melamine was isolated in 1834 and it wasn t until 1933 that Palmer Griffith produced dicyanamide and found that it contained melamine. The addition of formaldehyde produced a resin which could be compounded into a desirable molding compound. This new compound had a number of desirable quahties superior to phenolics and ureas of that time. The colorability and surface hardness led to its use in molded dinnerware along with some very important military and electrical applications. 

Urea-formaldehyde (UF) resins are mainly used as adhesives for wood. Laminated sheets (tables and counter tops) are a major application for melamine resins, which stay in the outer decorative surface. Molding compounds, their first big application, is still a major market, taking advantage of their extreme hardness and heat resistance. Coatings, textile finishing, paper additives, leather tanning and foundry binders, for which methanol- or butanol-etherified resins are usually employed, are important markets discussed in Ref 203. 

Phenolic resin (PF) is the technically most important representative of the class of condensafion resins, ft is created in several process steps from the monomer base materials carbolic acid and formaldehyde. Here, we distinguish between resols and novolacs. Phenolic resins are often processed in the form of free-flowing molding compounds under pressure at elevated temperatures individual cases of liquid processing are also known. Melamine resins, urea resins, and furan resins are also condensation resins created from formaldehyde. 

Urea-formaldehyde reaction products were described as early as 1908, but the first useful commercial product, a molding compound invented in England by Edmond C. Rossiter, did not arrive until almost 20 years later. It was a fairly complex formulation using purified cellulose fiber as reinforcement. The amino resin contained equimolar amounts of urea and thiourea. The new product could be supplied in light translucent colors. The molded products had a hard, stain resistant surface, and there was no objectionable phenolic odor. In short, the product was unique for its time. 

Collective term for resins that are capable of being cross-Unked. Terms, aminoplast and amino plastic, are also used. The materials are based on compounds containing NH2 group and formaldehyde. The representatives are urea-, melamine-, and dicyanodiamide-based resins used for laminating and molding. 

---