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On The Mechanisms Of Mechano-Sorptive Creep Reduction By Chemical Cross-Linking
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
Innventia AB.
Innventia AB.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.ORCID iD: 0000-0001-8622-0386
2009 (English)In: Advances in Pulp and Paper Research, Oxford 2009: Transactions of the 14th fundamental research symposium / [ed] S.J. I'Anson, Lancashire, UK: The Pulp and Paper Fundamental Research Society , 2009, 1001-1017 p.Conference paper, Published paper (Refereed)
Abstract [en]

Despite the technical importance of mechano-sorptive creep in paper, the exact mechanism behind this phenomenon is still not fully understood. In this study it was shown that the mechano-sorptive creep of paper sheets can be significantly reduced by chemical cross-linking through periodate oxidation. The mechanism behind this reduction has been examined through creep measurements of both sheets and individual fibres. For sheets the creep acceleration due to varying humidity was significantly reduced by the chemical cross-linking. For single fibres, however, the creep acceleration was not affected by the chemical crosslinking. In fact the absolute creep rate for the periodate oxidised fibres were higher than that of the reference fibres. This clearly showed that the improvement in mechano-sorptive creep found on a sheet level does not originate from an improved creep resistance for individual fibres but rather from mechanisms operating at the fibre network level. Hygroexpansion and moisture sorption of the sheets during the humidity cycling used for creep testing have also been measured, and the results showed that both was reduced by the periodate oxidation. Reduced moisture sorptivity and hygroexpansion probably minimises stress concentrations at the fibre network level and thereby also the creep acceleration.

Place, publisher, year, edition, pages
Lancashire, UK: The Pulp and Paper Fundamental Research Society , 2009. 1001-1017 p.
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-12315ISI: 000281142700029ISBN: 978-0-9545272-6-6 (print)OAI: oai:DiVA.org:kth-12315DiVA: diva2:309609
Conference
14th Fundamental Research Symposium on Advances in Pulp and Paper Research Location: St Annes Coll, Oxford, ENGLAND Date: SEP 13-18, 2009
Note
QC 20100616Available from: 2010-04-07 Created: 2010-04-07 Last updated: 2012-03-22Bibliographically approved
In thesis
1. Influence of fibre modification on moisture sorption and the mechanical properties of paper
Open this publication in new window or tab >>Influence of fibre modification on moisture sorption and the mechanical properties of paper
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fibre modification might be a way to improve the performance of paper, to increase its cost competiveness and enable new paper-based products to be developed. Therefore, the influence of fibre modification (with polyelectrolytes or by fibre cross-linking) on the mechanical properties of special importance for packaging paper grades was studied.

Creep deformation under varying humidity conditions (i.e. mechano-sorptive creep) is of outmost importance for the stacking life of paper-based boxes. The influence on creep behaviour of adsorbing polyallylamine (a cationic polyelectrolyte) to fibre surfaces or throughout the fibre walls was studied. Adsorption to fibre surfaces reduced the creep at constant humidity. The mechano-sorptive creep was not however influenced. The use of polyelectrolytes did not thus appear to be a feasible strategy for reducing mechano-sorptive creep.

Polyelectrolytes can however be efficient in improving other mechanical properties. The use of multilayers consisting of polyallylamine (PAH) and polyacrylic acid (PAA) was for example shown to significantly increase the strength of paper with much less densification and build-up of residual stress than is obtained by beating.

Cross-linking by oxidation with periodate radically decreased the mechano-sorptive creep of sheets made from the oxidised fibres. The basic mechanism behind the reduction in mechano-sorptive with cross-linking was found to be that the cross-linking slowed down the moisture sorption kinetics. A lower sorption rate led to smaller moisture content variations during the mechano-sorptive creep testing, and thus less sorption-induced swelling and stress concentrations at fibre/fibre joints. However, for cross-linking to be a practical way to reduce creep, the large problem of embrittlement must be solved.

The shear strength of couched sheets was measured to study the interaction between the sheets at different solids content. The shear strength was low until a solids content of approximately 60−70% was reached, which suggests that interactions important for the strength at complete dryness start to develop at this solids content. The effect of different fibre modifications and additives on how the fibres interact during the consolidation process is not always well understood. The method of shear strength determination could in the future be applied to modified fibres to hopefully increase the understanding of how different modifications influence the fibre/fibre interactions. A deeper understanding might reduce the time for the development of new and improved fibre modifications.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 84 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:11
Identifiers
urn:nbn:se:kth:diva-12318 (URN)978-91-7415-606-5 (ISBN)
Public defence
2010-04-23, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100616Available from: 2010-04-09 Created: 2010-04-07 Last updated: 2010-06-16Bibliographically approved

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