Study On The Synthesis And Properties Of Propionate Starch Used As Warp Sizing Agents

In order to improve the properties of esterified starch used as warp sizing agents, the paper clarified the influence of such technological variables as reaction medium, pH value, reaction temperature, reaction time and vinyl propionate amount on the esterification efficiency by using vinyl propionate as esterifying agent. The experimental result demonstrated that the variables considered showed evident effect on the reaction efficiency. The maximum efficiency of propionylation of starch with vinyl propionate was reached using sodium hydroxide as catalyst in an aqueous medium. Appropriate reaction conditions could be achieved as follows: 8～9 for pH value at about 40℃in aqueous medium for a reaction time of 6h.Moreover, the paper also clarified inherent relation between the sizing properties and modification extent, a series of propionylated starch with different degree of substitution (DS) were prepared using propionic anhydride as esterifying agent through varying the feed ratio of esterifying agent to starch. The experimental results showed that: the propionylation enhanced the adhesion of starch to polyester fibers and improved the breaking elongation, bent-fatigue resistance and abrasion resistance of starch film. As the DS value increases, the adhesion of propionylated starch to polyester fibers initially increases, reaches a maximal value at 0.019 and then decreases. However, the adhesion of propionylated starch to cotton fibers decreases when the DS value exceeds 0.01.The adhesion and film behaviors of propionylated starch were also evaluated by contrasting with acetylated starch to definite the differences of their sizing properties. When the DS value of propionylated starch was close to that of the acetylated, propionylated starch was superior in breaking elongation, bent-fatigue resistance and abrasion resistance of sizing film and contributed more to the adhesion-to-polyester fibers. That is, in case of obtaining certain value in the adhesion to fibers, the modified level of propionylated starch was much lower than that of the acetylated one. However, the modification level of the propionylated starch used as warp sizing agents should not be too high, a proper range of 0.01～0.032 in DS value is recommended based on this investigation.