Effect of pre-straining of paper sheet on its sizing efficiency.

The sizing efficiency of pre-strained papers were measured by Stockigt and Cobb sizing test methods. It was found that the sizing efficiency of acidic-sized papers decreases with straining of sheet, while that of alkaline-sized papers exhibits a reverse tendency. Straining level also affects sizing efficiency. However, all these changes are within 10% of the sizing degree of the unstrained paper. Effect of the factors being affected by straining, such as paper thickness and porous structure, were studied on the basis of Lucas-Washburn equation. Analysis shows that the differences between alkaline- and acidic-sized papers could be interpreted in terms of the bonding forces between pulp fibers and sizing agents, and the uniformity of distribution of the sizing agents on the fiber surfaces.