C-stage resin

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. 

See B-stage resin C-stage resin novolak phenol-formaldehyde resin. 

C-Stage resin. (resite). The fully cross-linked phenol-formaldehyde resin, which is infusible and insoluble in all solvents. 

Simple PF resins are readily attacked by sodium hydroxide. However, cresol-formaldehyde, and especially xylenol formaldehyde resins, are much less susceptible to attack. Resins are often more resistant to strong alkaline solutions (i.e., 15 to 20%) than to dilute solutions (i.e., 5%). The filler has a considerable influence on the chemical resistance of the resins. Inert mineral fillers have a better resistance than cellulosic fillers. C-stage resins are resistant to most acids, except sulfuric acid stronger than 50%, formic acid, and oxidizing acids such as nitric and chromic acids. The insolubility of hardened resins in acetone is used to test the degree of cure of the resin. The curing temperature influences the... 

Phenol-formaldehyde n. A condensation product of reaction of phenol and formaldehyde. If the reaction is carried under acidic conditions, the product formed is Novolac. Under alkaline conditions, with an excess formaldehyde, an C-stage resin is formed. Odian GC (2004) Principles of polymerization. John Wiley and Sons Inc., New York. Salamone JC (ed) (1996) Polymeric materials encyclopedia. CRC Press, Raton, FL. See image)... 

It may be mentioned here that it is common practice to refer to resols as stage resins and to the final network polymers as resits or C stage resins intermediate materials are called resitols oxB stage resins,... 

Two-pass coated foils have a C-stage resin layer against the foil and a B-stage layer for flow and fiU.The fuUy cured C-stage layer acts as a stop during the lamination process, typically enabling better thickness control. 

Resins that are primarily in the polymethylol noncondensed form are called A-stage resins and are easily soluble in water, alcohols and ketones. Further into the condensation, when dimers, trimers, and higher oligomers are formed, resins are labeled B-stage and finally, when curing, they are called C-stage resins. Resoles are insoluble and intractable resins... 

As with phenol-nitriles, a chemical reaction may occur but is less likely. The PF component converts to a C stage resin. 

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