In this study, the application of different dosages of low and high molecular weights (MW) of chitosan
(Ch), cationic starch (CS) and poly vinyl alcohol (PVA) were systematically investigated using old corrugated
carton (OCC) furnishes. Various sequences of above-mentioned polymeric additives were also
examined to find out the optimal combination for improving both wet and dry tensile strength. For
each treatment, 4 handsheets, each having basis weight of 100 g/m2, were made. In general, the tensile
strength of handsheets was significantly affected by the addition of polymeric agents. The enhancing
effect of additives on dry tensile property was much higher than wet condition. The results also showed
that the tensile strength of the samples made from OCC furnishes were improved upon the addition of
high molecular weight chitosan (ChI) compared to the untreated ones (control). The low MW chitosan
did not change the properties of handsheets dramatically. Application of polymeric agents moderately
decreased the stretch to rupture, however with increasing dosage the stretch was improved. Sequential
addition of used polymers showed that triple application of polymers was beneficial to both dry and wet
tensile strength, although the effect was larger for dry. The best results in wet and dry tensile strengths
were achieved using sequential of PVA-ChI-CS. Sequential addition of oppositely charged polymers forms
a macromolecular layered structure of polyelectrolytes.