Carboxymethyl cassava starch/polyurethane dispersion blend as surface sizing agent

Abstract

Surface sizing agent (SSA) is a material used to improve the surface quality of the paper. It is one of the compulsory components in the paper-related industries to impart surface smoothness, printability, water resistivity and brightness. An environmental friendly surface sizing agent based on carboxymethyl cassava starch/polyurethane dispersion (CCS/PUD) blend had been developed. A local cassava starch (CS) was modified with anionic reagent, sodium monochloroacetate (SMCA) via etherification, in a presence of sodium hydroxide (NaOH) to form sodium carboxymethyl cellulose (CCS). Later CCS was blended with 30 wt% polyurethane dispersion (PUD) to enhance its water resistivity. The CCS/PUD blend was applied onto the surface of a hand-made paper prior to being tested and characterised. Fourier transform infrared analysis had verified the successful of etherification process by showing peaks at 3,400 cm-1, 1,635 cm-1 and 1,440 cm-1, corresponding to carboxymethyl substituent. The highest degree of substitution (0.76) was obtained from the system that used 6 g SMCA at fixed 1 : 7 CS : Water ratio and 4 mL NaOH. Meanwhile, CCS/PUD-coated paper had improved water resistivity corresponded to higher water contact angle at 73°, in comparison with the CCS-coated paper (62°) and the uncoated paper (40°). This was supported with low surface energy showed by CCS/PUD-coated paper (33.9 mJ/m2).