Analysis of the Functional Groups Formed on the Corona-Treated Cellulose Fibre Sheet Surface by Means of Chemical Modification in Gas Phase-ESCA Technique.

Abstract

The surfaces of corona-treated cellulose fibre sheets were characterized by a chemical modification in gas phase-ESCA technique. Whatman #1 filter paper, handsheets from softwood bleached sulfate pulp (N•BKP), handsheets from hardwood bleached sulfate pulp (L•BKP) and handsheets from thermomechanical pulp (TMP) were prepared as cellulose fibre sheet samples. The following results were obtained. (1) Corona-treated cellulose fibre sheets were chemically modified (derivatized) in gas phase by pentafluorophenylhydrazine (PFPH) or trifluoroethanol (TFE), and ESCA spectra of the derivatized sheets were examined. The results show that carbonyl and carboxyl groups were formed on the surface of the cellulose fibre sheets. (2) The quantity of the introduced carbonyl and carboxyl groups, which were obtained by derivatization in gas phase, was larger than those obtained by derivatization in liquid phase. Furthermore, the quantities of the functional groups formed on the surface of the sheets by derivatization in gas phase after washing with some organic solvents and those by washing with organic solvents after derivatization were found to be less than those derivatizing only in gas phase. These results suggest that carbonyl and carboxyl groups were introduced onto the framework or main chain in the surface layer of the sheets. At that time, depolymerization occurs in the framework and the resulting fragmental low molecular compounds have carbonyl and carboxyl groups. (3) The total concentration of the carbonyl and carboxyl groups in the ethanol extracts from the corona-treated sheet were determined by oxime formation and hydroxamic acid-Fe chelate complex formation method, respectively. The increase of 0.98% in the carboxyl group for Whatman #1 filter paper and that of 0.58% for TMP handsheet were found, compared with those of untreated sheets. The increase of 0.02% in the carboxyl group for the Whatman #1 filter paper and that of 0.04% for the TMP handsheet were also found. These results indicate that the low molecular compounds were formed by corona discharge and the compounds possess carbonyl or carboxyl groups.