Electric conductivity of wet recycled paper sheets

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In order to develope quantitative determination of additives in recycled pulp, electric conductivity of wet pulp web and Fourier transform attenuated total reflection infrared (FT-IR-ATR) spectra of dry pulp sheet were investigated in this study. The concluding remarks for the paper sheets containing polyacrylamide (PAM) dry-strength additives and those further recycled are as followed.1.The electric conductivity of wet pulp sheet decreased with an increase of the PAM amount retained. The more cation amoumt in PAM increased the more the electric conductivity decreased.2.The electric conductivity of wet pulp sheet without PAM decreased on the first recycling and hardly changed by further recycling. On the other hand for the sheet with PAM,the electric conductivity hardly changed by any recycling.3.The difference ATR spectra between those of the sheets with and without PAM gave spectra of the PAM retained in the sheets. The absorbance of PAM characterizing band linearly increased with PAM content of the sheets irrespective of beating degree. Thus, a handy technique using FT-IR-ATR spectroscopy was proposed for determing the amount of PAM retained. Further, spectrum changes through the changes of ATR prism and beam angle indicated that PAM distribution very close to the pulp fiber surfaces irrespective of beating degree.4.The PAM retained in the sheets were gradually removed with an increase of the number of recycling procedures. The ratio of PAM removing was about 10% for a recycling. The decrease of tensile strength by recycling was large comparing with the decrease of PAM amount by recycling.