EFFECT OF CROSS-LINKING ON FUNCTIONAL-PROPERTIES OF CATIONIC CORN STARCH

Native corn starch was cross linked with phosphorus oxychloride (POCl3 ) before and after cationization to DS 0.04 in an aqueous ethanolic-al kaline solvent with no adverse effects on the cationization reaction r ate. Cross linking at six levels of POCl3 (7.5-120 mu l/50g starch) de monstrated that the gelatinization temperatures of cationic starch inc reased but enthalpies of gelatinization (Delta H) decreased in proport ion to the amount of added POCl3. Amylograph viscosities increased wit h level of POCl3 up to a maximum of 45 mu l POCl3 and then decreased m arkedly at higher concentrations of POCl3. At 30-45 mu l POCl3, the am ylograph viscosities of cationic corn starch increased very rapidly an d remained uniformly high throughout the rest of the heating and cooli ng cycle. At this level of cross linking and cationization, the modifi ed starch could be used industrially as an adhesive or in paper manufa cture at more dilute concentrations and with less energy input for mix ing the slurry than would be required for cationic starches which exhi bit high peak viscosities but negative setbacks on cooling.