The Effect of Degree of Substitution of Cationic Starch on Multi-layer Formation of Ionic Starches in Recycled Fibers

Document Type : Research Paper

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Abstract

Layer-by-layer self-assembly technique is a novel method in nanotechnology for modifcation of the surface properties of solid materials. Among these materials cellulosic fbers can undergo surface changes by formation of polyelectrolyte multi-layers (PEM) using layer-by-layer method. In this study, the effect of degree of substitution of cationic starch on multi-layer build up of cationic and anionic starches and on the bonding ability of the waste corrugated container (OCC) recycled fber with layer-by-layer  technique was  investigated. Experiments were  conducted  at pH≈7.5 and 750 rpm stirring rate in a dynamic drainage jar (DDJ) for 10 min deposition time to  construct 1  to 8  consecutive  layers. The handsheets  at 60 g/m2 on weight basis were made with untreated and  layer-by-layer  treated fbers and  their strengths have been evaluated. The results showed that the interbonding ability indices of fbers such as  tensile  index and  internal bonding  improved signifcantly with multi-layering of cationic starch. However, there was no meaningful change in quality of the specimens formed. Compared to the untreated fbers, the tensile index of cationic starch increased by 129% at 7th layer with DS≈0.045 and internal bonding increased by 400% at the 5th  layer. Moreover, with  regard  to  different  degrees  of  substitution  of  starch,  the increasing  trend  in properties was observed;  in which DS≈0.018  for  lower number of layers and DS≈0.045 for higher number of layers. In the frst case, more starch of lower DS was needed to neutralize the charge of the fber surface but in the second case greater charge balance of two polymers resulted in further adsorption and greater stability of cationic starch layer, and consequently higher strength has been achieved for the obtained paper.

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Iranian Journal of Polymer Science and Technology
Volume 25, Issue 1 - Serial Number 1
May and June 2012
Pages 11-18

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