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

Layer-by-layer self-assembly technique is a novel method in nanotechnology for modification of the surface properties of solid materials. Among these materialscellulosic fibers can undergo surface changes by formation of polyelectrolytemulti-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 starchesand on the bonding ability of the waste corrugated container (OCC) recycled fiber 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 fibers and their strengths have been evaluated. The results showed that the interbonding ability indices of fibers such as tensile index and internal bonding improved significantly with multi-layering of cationic starch. However, there was no meaningful change in quality of the specimens formed. Compared to the untreated fibers, 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 first case, more starch of lower DS was needed to neutralize the charge of the fiber 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.