Mixing of oxidized starch and polyvinyl alcohol for surface sizing of paper.

Surface sizing chemical (mostly oxidized or enzymatically modified starch) flows into the pores of cellulose network and also remains on the surface affecting the surface and intrinsic properties of paper. Polyvinyl alcohol (PVA) can be used for surface sizing because it is a water soluble polymer and has high film forming ability. Due to economic constraints, using PVA alone for surface sizing is not a good option. Current study explored the effects of using oxidized starch and PVA in mixed ratios (80:20, 50:50 and 20:80) on mechanical and surface properties of paper. The surface sizing with sizing weight of 3.5±0.3 g/m2 was done. The results of the study showed that the breaking length, burst index, air permeance, gloss, Cobb60 and optical properties like brightness, whiteness, flouroscence of paper were better for mixed ratios in comparison to only oxidized starch. After surface sizing with PVA, the value of air permeance (time of air leak) was increased to 200 Gurley second in comparison to 9 only for base paper. Surface sizing with blends of oxidized starch solution and PVA solution i. e. 80S+20P, 50S+50P and 20S+80P increased the time of air leak by 900%, 1455% and 1788%, respectively in comparison to base paper.