コロナ放電処理によるセルロース繊維シート物性の変化

Abstract

Whatman # 1 filter paper, handsheet from softwood bleached sulfate pulp (abbreviated as NBKP hereafter), handsheet from thermomechanical pulp (abbreviated as TMP hereafter) and regenerated cellulose film were treated with 401 watts/m2 of corona discharge for the duration of 0 to 180 min. Some changes were examined in the SEM images of the cellulose fibre sheets, in the sheet strength and in the sheet porosity by the increase in the duration of the corona treatment. The following results were obtained.(1) The SEM images changed with the Whatman # 1 filter paper, the handsheet from NBKP and the handsheet from TMP. That is, perforation or boring occurred in the case of the higher duration of 30 min. and 60 min. But, no changes occured with the regenerated cellulose film, as the duration of the corona treatment increased.(2) The tensile index and Young's modulus of the fibre sheets decreased gradually but significantly with the increase in duration of the corona discharge treatment. At that time, the zero span tensile strength also decreased slightly. The tensile index and tensile modulus decreased also in the case of regenerated cellulose film with the increase in the duration.(3) As the duration of corona treatment increased, the cellulose fibre sheets became more permeable. The porosity and mean pore radius obtained by the mercury intrusion method also increased with the increase in the duration. However, no changes occured in permeability with the regenerated cellulose film, even in the duration of 180 min.From the above-described facts, the corona-induced defects is considered to partly bring about the decrease in the cellulose fibre sheet strength.Another mechanism should be considered further from the fact that the tensile strength and the tensile modulus decreased with the increase in the duration for the regenerated cellulose film. A certain fraction of the more microscopical framework which resists against an external force, must be degradated by the oxidation processes. Both mechanism are proposed to affect the reduction in cellulose sheet strength by the corona treatment for a long duration. At the present state, the importance of the two mechanisms cannot be estimated for the reduction in the sheet strength.