A-stage resin

Stopping the polymer at this point requires the ratio of formaldehyde to phenol to be less than unity. Both methylene and ether bridges are known to be present. The reaction is either acid or base catalyzed, and branching is uncommon at this stage. The products are variously known as A stage resins, novolacs, or resole prepolymers. 

Key resins used in the manufacture of laminates are made with formaldehyde (qv). The A-stage resins are manufactured to have low levels of free formaldehyde, less than one percent, and plant atmospheres as well as individual operators are monitored to be certain they are exposed to levels of formaldehyde that are below OSHA guidelines of 0.75 ppm (14). 

Baekeland found that a relatively stable resole prepolymer could be obtained by the controlled condensation of phenol and formaldehyde under alkaline conditions. These linear polymers of phenol-formaldehyde (PF) may be converted to infusible cross-linked polymers called resites by heating or by the addition of mineral acids. As shown in structure 4.80, the initial products obtained when formaldehyde is condensed with phenol are hydroxybenzyl alcohols. The linear resole polymer is called an A-stage resin, and the cross-linked resite is called a C-stage resin. 

B-stage Advanced A-stage resin, carbamate A urethane. 

After about 20 min, the formation of di- and trimers begins to yield the so-called A stage resin in which melamine is linked via methyleneether and methylene bridges (see Scheme 2). This A stage resin is then impregnated into d6cor paper by means of an impregnation line. 

See A-stage resin B-stage resin C-stage resin novolak Baekeland, L. H. phenolic resin. 

In the A stage, simple PF resins are readily soluble in alcohol, esters, ketones, phenols, and some ethers, and insoluble in hydrocarbons and oils. As a class, resols tend to be more soluble in alcohols and water, and novolaks tend to be more soluble in hydrocarbons. In the early stages of condensation, resols are often soluble in water, owing to the presence of methylolphenols, especially polyalcohol. This is more pronounced with resols that are derived from phenol. Cresilic resols are less soluble, and xylenolic resols are almost insoluble in water. The solubility of A-stage resins in dilute aqueous sodium hydroxide or in mixtures of water and alcohols follows the same trend. 

Synonyms Alkyl-phenol formaldehyde resin A-stage resin Novolac resin Novolak resin One-stage resin PF Phenol-formaldehyde Phenol-... 

Resol resin A-stage resin Two-stage resin... 

See Cocamide DEA Stafoam DFC. See Cocamide MEA Stafoam DL. See Lauramide DEA Stafoam DO, DOS. See Oleamide DEA Stafoam F. See Cocamide DEA Stafoam L. See Lauramide DEA Stafoam MF. See Cocamide MEA Staform P. See Gum ghatti A-stage resin. See Phenolic resin Stainless steel CAS 12597-68-1 Synonyms Steel, stainless Definition Group of corrosion resistant steels containing at least 10% chromium and may contain other alloying elements maintains... 

Resoles andNovolacs. There are two types of phenolic A-stage resins resoles and novolacs (Fig. 3.7). Resoles have many methylol groups that make them water soluble and highly reactive novolacs are stable ohgomers, which can be cross-linked by adding more formaldehyde. Therefore, they are sometimes referred to as one-step and two-step resins, respectively. 

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