Problems in the Determination of Cured, Phenol-Formaldehyde Resins in Paper and Wood

Analysis for cured phenol-formaldehyde resin in treated paper usually involves removing the cellulose with 72 percent sulfuric acid leaving the lignin and resin; this is followed by treatment with sodium chlorite plus acetic acid at 60 ?C to remove the lignin and yield the insoluble resin residue. This method is subject to severe errors: (1) Action of the sulfuric acid causes losses in the cured resin (no paper present); (2) Impregnating of cured resin into cellulose fibers prevents access to the fiber by the acid and results in a considerable amount of unhydrolyzed paper; and (3) Up to 14.7 percent of the cured resin (no paper) was dissolved by the sodium chlorite treatment. Errors due to the presence of unhydrolyzed cellulose and the losses of resins produce results that may be off by 30-40 percent.

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