STRUCTURE OF STARCH-BENTONITE GELS

Mixed gels of starch and bentonite are investigated in the interval 0. 056-0.089 of total solids/water ratio and 0-100% starch in the solids. The bentonite was a sodium calcium bentonite with a Na/Ca ratio of 1. 76. In water it forms gels consisting of a network of band-type struct ures. Starch forms gels through hydrogen bonds between granules and/or amylose and amylopectin present on the external surfaces of granules and/or in fully stretched form. Mixed gels of bentonite and starch wer e obtained by adding corn starch granules to the already formed benton ite gels and heating the mixture above the Kofler gelatinization tempe rature. Amylose and amylopectin were adsorbed on strands of band-type structures of montmorillonite lamellae. Starch gellation, e.g. diffusi on of amylose out of the granule, was facilitated in the presence of b entonite, On the other hand. the presence of starch favored delaminati on of the montmorillonite particle into thinner lamellae, Maximum gela tinization and polymer adsorption were observed for gels with 20% star ch and 80% bentonite. Montmorillonite networks formed the continuous p hase for 0-80% starch, At higher starch concentrations. montmorillonit e flakes were dispersed within the polymer network. increase in the wa ter content of the gels caused segregation of the bentonite and starch .