AbstractThe impact of montmorillonite (nanoclay) addition on the mechanical and morphological properties of paper made from neutral sulfite semichemical (NSSC) and old corrugated container (OCC) pulps was evaluated in systems utilizing cationic starch for dry-strength. The nanoclay amount was considered at five levels, and cationic starch was applied at a 1% level. In OCC pulp, by increasing the nanoclay up to 4%, the tensile index and corrugating medium test (CMT) were increased; however, there was a decrease when the nanoclay was increased to 8%. By increasing the nanoclay to 2%, the tear and burst indexes and ring crush test (RCT) increased, but there was a reduction when the nanoclay was increased to 8%. Average air resistance tended to increase as the nanoclay was increased to 8%. In the case of NSSC pulp, by increasing the nanoclay amount from 0 to 8%, the average tensile, tear, and burst indexes decreased, while the air resistance increased. The CMT amount increased with increasing nanoclay content to 2%, but a reduction was seen for other levels. The RCT exhibited an increase with increasing nanoclay up to 4%, after which it decreased. Results suggest that the proportion of nanoclay added with cationic starch needs to be optimized, depending on furnish conditions.