The effect of cationic starch degree of substitution on nanoparticle system performance in old corrugated containers recycling

Cationic starch has been widely used with various mineral nanoparticles such as nanosilica, in wet-end of papermaking. This study was aimed to study the effect of cationic starch with different degrees of substitution (DS: 0.018 and 0.045) in nanoparticle containing system with nanosilica, in recycled OCC pulp. In this respect, initially, to study the shape and dimensions of nanosilica sol particles, atomic force microscopy (AFM) and transmission electron microscopy (TEM) was used; thereby the average size of nanosilica sols were measured less than 50 nm. Moreover, in order to study the papermaking process parameters, the results revealed that high DS cationic starch (0.045) resulted more effective interactions with silica nanoparticles, so that, an increase in drainability of the furnish from 300 ml CSF for blank sample to about 560 ml CSF, was observed. In addition, as the internal bonding strength of paper can be a proper indicator of the starch performance, the effect of cationic starch DS was more prominent in the case of this strength index; such that, following application of high DS cationic starch, the internal bonding strength was raised more than twice as much. On the other hand, generally, although, due to electro-kinetics of cationic starch adsorption, reversing the charge of the whole paper-making system can be as a limiting factor for application of high DS cationic starch, but, in OCC recycling production lines, application of high DS cationic starch was much more effective.