Urea-formaldehyde resin condensation polymers

The reaction conditions can be varied so that only one of those monomers is formed. 1-Hydroxy-methylurea and l,3-bis(hydroxymethyl)urea condense in the presence of an acid catalyst to produce urea formaldehyde resins. A wide variety of resins can be obtained by careful selection of the pH, reaction temperature, reactant ratio, amino monomer, and degree of polymerization. If the reaction is carried far enough, an infusible polymer network is produced. 

In far too many instances trade-name polymer nomenclature conveys very little meaning regarding the structure of a polymer. Many condensation polymers, in fact, seem not to have names. Thus the polymer obtained by the step polymerization of formaldehyde and phenol is variously referred to a phenol-formaldehyde polymer, phenol-formaldehyde resin, phenolic, phenolic resin, and phenoplast. Polymers of formaldehyde or other aldehydes with urea or melamine are generally referred to as amino resins or aminoplasts without any more specific names. It is often extremely difficult to determine which aldehyde and which amino monomers have been used to synthesize a particular polymer being referred to as an amino resin. More specific nomenclature, if it can be called that, is afforded by indicating the two reactants as in names such as urea-formaldehyde resin or melamine-formaldehyde resin. 

Plywood and particle board are often glued with cheap, waterproof urea-formaldehyde resins. Two to three moles of formaldehyde are mixed with one mole of urea and a little ammonia as a basic catalyst. The reaction is allowed to proceed until the mixture becomes sympy, then it is applied to the wood surface. The wood surfaces are held together under heat and pressure, while polymerization continues and cross-linking takes place. Propose a mechanism for the base-catalyzed condensation of urea with formaldehyde to give a linear polymer, then show how further condensation leads to cross-linking. (Hint The carbonyl group lends acidity to the N—H protons of urea. A first condensation with formaldehyde leads to an inline, which is weakly electrophilic and reacts with another deprotonated urea.)... 

While catalysts are also used in the production of other types of polymers, the properties of most of these materials are not particularly dependent on the type of catalyst employed. Many poly condensation reactions, e. g. the formation of polyesters, polyamides or urea-formaldehyde resins, are speeded up by addition of some Bronsted or Lewis acids. Since relevant properties of these polymer products, such as their average chain lengths, are controlled by equilibrium parameters, primarily by the reaction temperatures and molar ratios of the monomers employed, and since their linkage patterns are dictated by the functional groups involved, addition of a catalyst has little leverage on the properties of the resulting polymer materials. 

A large number of commercially important condensation polymers are employed as homopolymers. These include those polymers that depend on crystallinity for their major applications, such as rylons and fiber-forming polyesters, and the bulk of such important thermosetting materials like phenolics and urea-formaldehyde resins. In many applications, condensation polymers are used as copolymers. For example, fast-setting phenolic adhesives are resorcinol-modified, while melamine has sometimes been incorporated into the urea-formaldehyde resin structure to enhance its stability. Copolyesters find application in a fairly broad spectrum of end uses. 

Formaldehyde/urea condensate Formaldehyde/urea copolymer Form-aldehyde/urea polymer Formaldehyde/urea precondensate Formaldehyde/urea epolymer Formaldehyde/urea resin. See Urea-formaldehyde resin... 

Urea, (p-ethoxyphenyl)-. See Dulcin Urea, 1,3-ethylene. See 2-lmidazolidinone Urea/formaldehyde adduct Urea/formaldehyde condensate Urea/formaldehyde copolymer Urea/formaldehyde oligomer Urea/formaldehyde polymer Urea/formaldehyde precondensate Urea/formaldehyde prepolymer. See Urea-formaldehyde resin Urea-formaldehyde resin CAS 9011-05-6... 

A polymer obtained in step-growth polymerization, often accompanied by elimination of small molecules (e.g., water). Polyesters, polyamides, phenol-, melamine-, and urea-formaldehyde resins are typical condensation polymers. 

Urea-formaldehyde resin (UF) is a hydrophilic condensation polymer. The UF monosized non-porous microspheres were prepared with (-I-) L-2-amino-5-ureidopentanoic acid as the chiral ligand. The micro-spheres exhibited exceptional mechanical strength, chemical stability in the pH range 1-13, and low tendency toward swelling in solvents they were used for the CLEC separation of amino acids. Later, the porous UF microspheres were also prepared and L-proline was grafted via epichlorohydrin onto the polymer (l-proline content 0.28 mmol/g). Eighteen D,L-amino acids were resolved on the sorbent with aqueous ammonia... 

Urea-formaldehyde resin (UF) is a hydrophilic condensation polymer. The UF monosized nonporous microspheres were prepared with (-i-) L-2-amino-5-ureido-... 

Diffusion and Penetration. Thermosetting condensation polymers such as phenol-formaldehyde and urea-formaldehyde resin systems generate water as a byproduct of cure. If water also is the solvent, it is a requirement that the solvent water diffuse into the wood to lower the concentration of water at the interface which might otherwise inhibit cure. Water, or other solvent(s) if present, will cany mobile lower molecular weight polymer fractions into the cell interstices and cell walls. This chromatographic effect is the initiation of penetration. 

Formaldehyde may react with the active hydrogens on both the urea and amine groups and therefore the polymer is probably highly branched. The amount of formaldehyde (2—4 mol per 1 mol urea), the amount and kind of polyamine (10—15%), and resin concentration are variable and hundreds of patents have been issued throughout the world. Generally, the urea, formaldehyde, polyamine, and water react at 80—100°C. The reaction may be carried out in two steps with an initial methylolation at alkaline pH, followed by condensation to the desired degree at acidic pH, or the entire reaction may be carried out under acidic conditions (63). The product is generally a symp with 25—35% soHds and is stable for up to three months. 

The first synthetic plastics were the phenol-formaldehyde resins introduced by Baekeland in 1907 [1], Melamine and urea also react with formaldehyde to form intermediate methylol compounds which condense to cross-linked polymers much like phenol-formaldehyde resins. Paper, cotton fabric, wood flour or other forms of cellulose have long been used to reinforce these methylol-functional polymers. Methylol groups react with hydroxyl groups of cellulose to form stable ether linkages to bond filler to polymers. Cellulose is so compatible with these resins that no one thought of an interface between them, and the term reinforced composites was not even used to describe these reinforced systems. 

A series of compounded flame retardants, based on finally divided insoluble ammonium phosphate together with char-forming nitrogenous resins, has been developed for thermoplastics.23 These compounds are particularly useful as intumescent flame-retardant additives for polyolefins, ethylene-vinyl acetate, and urethane elastomers. The char-forming resin can be, for example, an ethyle-neurea-formaldehyde condensation polymer, a hydroxyethyl isocyanurate, or a piperazine-triazine resin. Commercial leach-resistant flame-retardant treatments for wood have also been developed based on a reaction product of phosphoric acid with urea-formaldehyde and dicyandiamide resins. 

The broadest classification for plastics is the old thermoplastic and thermosetting . Examples of the former group are polyethylene, polystyrene, and poly-(methyl methacrylate) examples of the latter are urea-formaldehyde condensation polymers, powder coatings based on polyesters, epoxy resins, and vulcanized synthetic elastomers. 

Formaldehyde is employed in the production of aminoplasts and phenoplasts, which are two different but related classes of thermoset polymers. Aminoplasts are products of the condensation reaction between either urea (urea-formaldehyde or UF resins) or melamine (melamine-formaldeliyde or MF resins) with formaldehyde. Phenoplasts or phenolic (phenol-formaldehyde or PF) resins are prepared from the condensation products of phenol or resorcinol and formaldehyde. 

Another example of the improvement of properties of condensation polymers through copolymerization is illustrated by recent work with urea-formaldehyde (UF) resins. The preponderance of wood adhesive... 

Aminoresins or aminoplastics cover a range of resinous polymers produced by reaction of amines or amides with aldehydes [14,46,47]. Two such polymers of commercial importance in the field of plastics are the urea-formaldehyde and melamine-formaldehyde resins. Formaldehyde reacts with the amino groups to form aminomethylol derivatives which undergo further condensation to form resinous products. In contras to phenolic resins, products derived from urea and melamine are colorless. 

The urea-formaldehydes (UFs) are the most important and most used class of amino resin adhesives. Amino resins are polymeric condensation products of the reaction of aldehydes with compounds carrying aminic or amidic groups. Formaldehyde is by far the primary aldehyde used. The advantage of UF adhesives are their (1) initial water solubility (this renders them eminently suitable for bulk and relatively inexpensive production), (2) hardness, (3) nonflammability, (4) good thermal properties, (5) absence of color in cured polymers, and (6) easy adaptability to a variety of curing conditions [1,2]. 

Glyoxal/urea/formaldehyde condensate Glyoxal/urea polymer insolubilizer, textile finishing agents Zirconium butoxide insolubilizer, vinyl polymer Methacrylatochromic chloride instrument housings Phenol-formaldehyde resin instrument indicator fluid Mercury... 

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