Home » Volume 31, 2016 » Issue No. 3
On the nature of joint strength of paper − Effect of dry strength agents – Revisiting the Page equation
Tom Lindström, Innventia AB, Stockholm, Sweden, Christer Fellers, Sweden, Mikael Ankerfors, BillerudKorsnäs AB, Solna, Sweden and Gunborg Glad-Nordmark, Innventia AB, Stockholm, Sweden
This report deals with the effects of various chemical-treatments − carboxymethylcellulose-grafted (CMC) pulp in different ionic forms (Na+, Ca2+, and Al3+), cationic starch, anionic polyacrylamide, and microfibrillated cellulose (MFC) as well as PFI-refining on the strength properties of never-dried bleached soft-wood kraft pulp. The general in-plane strength properties were measured together with z-strength and interlaminar shear strength. The sheet density was varied by pressing the wet sheets to various dry solids content. The relative bonded area of the sheets was determined by the BET surface area of the sheets using krypton adsorption.
Interlaminar shear strength is introduced as a measure for fibre-fibre bond strength and validates its use in the Page equation from first principles and it was shown to hold over a large range of tensile strengths. Only at very high tensile index values the calculated tensile index deviated from measured tensile index. This was most likely due to a shift from adhesive to cohesive failure of the joint. The various strength reinforcement methods used were all based on carbohydrate based additives and for those additives the specific joint strength was found to be independent of the specific additive, so the strength reinforcement is only related to the increased relative bonded area upon the addition of the strength adjuvant, although the additives consolidate the sheet on various structural levels.
BET surface area, Carboxymethyl cellulose (CMC), Cationic starch, Fibre-fibre bonding, Interlaminar shear strength, Ionic groups, Joint strength, Microfibrillar cellulose, Nanofibril, Nanofibrillar cellulose, Page equation, Z-strength
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Nordic Pulp & Paper Research Journal (NPPRJ) is an international scientific magazine covering science and technology for the areas of wood or bio-mass constituents, pulp and paper and including new fiber-based materials, recovery and by-products from pulping processes, bio-refining and energy issues. Articles meeting required scientific standards are accepted from any continent.
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ISSN: 0283-2631