Influence of polymeric additives on short-time creep of paper
2007 (English)In: Nordic Pulp and Paper Research Journal, ISSN 0283-2631, Vol. 22, no 2, 217-227 p.Article in journal (Refereed) Published
Cationic polyallylamine (PAH) and cationic starch were adsorbed to unbleached softwood kraft pulp fibres in order to study the effect of these additives on the creep properties of the resulting paper sheets. For the fibres treated with PAH, the effect of molecular mass, adsorbed quantity and heat treatment of the prepared sheets at 160 degrees C was also studied. PAH was found to not influence the sheet density, whereas starch addition induced moderate densification. Both additives produced major improvements in dry strength measurements as stress and strain-at-break. PAH-treated sheets also showed a relatively small but statistically significant improvement in tensile stiffness, unlike starch-treated sheets in which the improvement was too small to be statistically significant. As expected. there was an inverse relationship between the adsorbed amount and the molecular mass of the PAH. However, for comparable adsorbed amounts, the molecular mass made no detectable difference to the mechanical properties. PAH was also labelled with fluorescein isothiocyanate and adsorbed to the pulp fibres. Examination of the fibres with a confocal scanning laser microscope revealed that the different molecular mass fractions adsorbed only to the exterior parts of the fibres (i.e. the molecules did not penetrate throughout the fibre wall). The creep behaviour of the paper sheets was evaluated under tensile loading using a specially designed testing apparatus, in both 50% RH and 90% RH at 23 degrees C. Strain was monitored as function of time and applied load. PAH was found to lower both instantaneous and time-dependent deformation during the relatively short measuring time of 100 seconds used in this work. Cationic starch had little or no effect on creep. Thus it is clearly demonstrated that PAH treatment of fibres results in sheets with a lower creeping tendency over short periods compared to sheets made with non-treated and starch-treated fibres.
Place, publisher, year, edition, pages
2007. Vol. 22, no 2, 217-227 p.
creep; mechanical properties; polyallylamine; cationic starch; confocal fluorescence microscopy
Paper, Pulp and Fiber Technology
IdentifiersURN: urn:nbn:se:kth:diva-7717DOI: 10.3183/NPPRJ-2007-22-02-p217-227ISI: 000248057800011ScopusID: 2-s2.0-34547345846OAI: oai:DiVA.org:kth-7717DiVA: diva2:12825
QC 201006162007-11-252007-11-252010-08-11Bibliographically approved