Effects of polysaccharides on the properties of Chinese lacquer sap

Raw lacquer sap was modified by the addition of small amounts of 2 wt% polysaccharide (lacquer polysaccharide, chitosan, carboxymethyl cellulose and sodium alginate) aqueous solution. The polysaccharide-modified lacquer saps dried faster than raw lacquer sap at a high relative humidity of 80%. The drying property strongly depended on the structure of polysaccharides and the drying time was in the order of chitosan < carboxymethyl cellulose < sodium alginate < lacquer polysaccharide. All lacquer saps did not dry at a very low relative humidity of 16%. However, when the relative humidity was adjusted to 70%, the polysaccharide-modified lacquer saps dried, while the raw lacquer sap did not. This difference was probably due to stronger hydrophilicity of polysaccharide-modified lacquer films' surfaces. In addition, the addition of polysaccharides greatly improved the gloss of lacquer films, but had little effects on the thermal, mechanical and chemical resistance properties of lacquer films.