Rheological properties of concentrated solutions of carboxymethyl starch

Abstract

Carboxymethyl starch was synthesized by the esterification of starch with monochloroacetic acid in ethanol as a reaction medium. Three samples of carboxymethyl starch having different degrees of substitution were prepared. The influence of temperature on the viscosity of concentrated carboxymethyl starch solutions, as well as the dynamic-mechanical properties of the concentrated solutions were investigated. The activation energy of viscous flow was determined and it was found that it decreased with increasing degree of substitution. The results of the dynamic-mechanical measurements showed that solutions of starch and carboxymethyl starches with higher degrees of substitution behave as gels. Values of the storage modulus in the rubbery plateau were used to calculate the molar masses between two points of physical crosslinking, the density of crosslinking and the distance between two points of crosslinking

the shape and size of macromolecules of carboxymethyl starch in diluted solutions

“…Postoji veliki broj radova u kojima je ispitivano ponašanje kako razblaženih tako i koncentrovanih rastvora skroba [4][5][6][7][8][9][10][11][12]. O ponašanju karboksimetil skroba u razblaženim rastvorima jako se malo zna iako se već duže vreme vrše istraživanja kako na polju sinteze, [1-3,13--15], tako i reoloških svojstava [13,14,16] karboksimetil skroba.…”