DIMENSIONAL STABILITY PROFILE OF COPY PAPER FORMED
IN HIGH MD-CD TENSILE STRENGTH RATIO CONDITION
Authors: Afonso H. T. Mendes1,2, Song W. Park1
1. University of São Paulo, São Paulo, Brazil
2. Centre Consultoria, Engenharia e Treinamento Ltda, Campinas, Brazil
ABSTRACT
Copy paper used in photocopiers, laser printers and similar devices
normally requires lower fi ber-orientation indexes, to provide certain
“squareness” to the sheet, for enhanced dimensional stability. Due
to the anisotropic nature of fi bers, a highly-oriented paper formation
will leverage the cross-machine hygroexpansivity due to increased
web shrinkage in the drying phase of production. This paper presents
the transverse profi le of CD dimensional stability of reprographic
paper manufactured in commercial gap former machine, from 100%
eucalyptus chemical pulp at high speed and set for operation at high
level of paper anisotropy (>3). The results of CD hygroexpansivity,
and shrinkage measurements obtained by image analysis
technique, showed the adverse effect of such operating condition
on dimensional stability of paper and corresponding anisotropic
level of paper web consolidation, both revealed by high levels of
hygroexpansion (>0.7%) and CD shrinkage (>8%) at the edge zones,
making a signifi cant portion of the web improper for high quality
demanding applications of end users. This insight can lead to future
actions in order to seek for new setup of paper machine operational
parameters and control web anisotropy index toward better paper
quality.
Key-words: anisotropy, gap former, hygroexpansivity, image
analysis, shrinkage.
O PAPEL vol. 79, num. 9, pp. 91 – 97 – SEP 2018
