A Comparison on the performance of cationic starch in external and internal applications for recycled linerboard

SStarch derivatives are as the most common additives required in the paper industry to increase paper strength, and for other various applications. Although both starch addition to the stock (internal application) and surface treatment of the board with starch (surface application) have limitations in applications and also different effects on paper products properties. But both of mentioned methods can be performed with the purpose of improving the mechanical properties of recycled linerboard. Therefore, in the current research, the effect of adding cationic starch to the pulp and also using the same amount of cationic starch for surface application on mechanical properties of recycled linerboard and water absorption (Cobb test) were comparatively evaluated. The results showed that, surface treatment of the paperboard clearly caused 30-45% increment in bending strength. Furthermore, internal application of cationic starch totally showed higher tensile strength index in comparison with surface application of cationic starch. However, there was not significant difference between paper tear index value by applying cationic starch in papermaking.