AN INFRARED SPECTROSCOPIC STUDY OF CHEMICALLY MODIFIED CHEMITHERMOMECHANICAL PULP

FT-IR spectroscopy was used to characterize chemically modified wood p ulp and to judge the efficiency of different pulp modification process es. Treatment of wood pulp with aliphatic anhydrides was shown to be m ore effective in a polar solvent such as DMF compared to a non-polar o ne typified by xylene. The esterification of hydroxyl group associated with the cellulosic material was indicated by the characteristic abso rption bands of the resulting cellulosic esters; the degree of hydroxy l conversion was determined by the ratio of peak intensity of hydroxyl and carbonyl stretching vibrations. The so-called ''Infrared Acetyl I ndex'' was shown to give a linear correlation with the gravimetrically determined anhydride uptake. Isocyanate modification of wood pulp yie lded more complex infrared spectra, because of various secondary react ions of the reactive isocyanate component. Various aromatic isocyanate s, used for chemical treatment of the wood pulp, led mainly to urethan e formation, as evidenced by the spectra of the modified pulp. The pre sence of polyurea or urea as the main reaction product of aromatic iso cyanates, postulated by a number of authors, could not be confirmed. N evertheless, phenylisocyanate treatment, at high concentration of isoc yanate and without purification of the modified pulp, led to the appea rance of at least one more reaction product in the pulp spectra, which is presumed to be either triphenylisocyanurate, the trimerization pro duct of phenylisocyanate, or carbanilide.