The effect of different strength additives on the strength development of wet web
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Helsinki University of Technology |
Diplomityö
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Date
2007
Department
Major/Subject
Puunjalostuksen kemia
Mcode
Puu-19
Degree programme
Language
en
Pages
88
Series
Abstract
To study the effect of strength additives on the strength development of web during drying, the tensile strength of webs treated with polymers was tested with an installation, which included a MTS tensile tester, IR dryer and on-line moisture measurement. The development of drying tension was also measured with this installation. The strength properties of samples dried with frame drying were measured to make comparison with the results of strength development test. The polymers used in this experiment were polysaccharides that can be separated into neutral polymers (xyloglucan and guar gum), weak cationic polyeletrolyte (chitosan), strong cationic polyelectrolyte (cationic starch), weak anionic polyelectrolyte (CMC) and weak polyelectrolyte multilayer (CMC and chitosan). The polysaccharides with different properties were used to compare their effect on the strength development during drying. According to strength development test, the interfibre bonding was the main factor influencing the modulus, drying tension, and tensile strength during drying. The interfibre bonding began to form at 45% solids when webs started to be dried. The properties and conformation of adsorbed polymers should have great effect on the water removal and strength development of wet webs during drying. At solids lower than 65%, the breaking strain should be determined by the elastic deformation of polymers. With increasing solids, the adsorbed polymers should change from elastic to plastic complex. The adsorbed polymers should increase the break strain by connecting more sub-structure into fibre network and not by the plastic deformation of adsorbed polymers. The polymer conformation should also have large effect on the paper strength, not only influenced by the hydroxyl group content of the polymers.Description
Supervisor
Laine, JanneThesis advisor
Myllytie, PetriHolappa, Susanna
Keywords
strength development, strength additives