Effect of calendering on physical and mechanical properties of coated papers

The purpose of this study was to improve properties of the coated papers by calendering. Two types of printing and writing paper (75 and 125gsm) and five coating suspensions (the first suspension with 22.9% binders and 50% solids content, the second with 24.73% binders and 50% solids, the third one with 22.9% binders and 30% solids, fourth suspension with a 24.73% binders and 30% solids and the fifth suspension with 42.3% binders and 50% solids content) were used. The coatings were composed of 80% kaolin clay, 20% ground calcium carbonate, dispersant and different ratios of polyvinyl acetate and lactic acid. The base and coated papers were dried after coating. The calendering treatment was carried out at a temperature of 55° C and 60 kg/cm linear pressure. Air resistance, thickness, water absorption, tearing resistance and bursting strength of papers were determined. The calendering operation was effective in reducing the thickness and increasing the air resistance. Water absorption was decreased only in 75gsm samples. In the effect of calendering the mechanical properties were improved slightly, but in most cases, had an adverse effect on the mechanical indexes.