Effect of Gelation Concentration on Tensile and Stress Relaxation Behavior of κ-Carrageenan Hydrogels

Abstract

The uniaxial stretching and the stress relaxation measurements were carried out for κ-carrageenan hydrogels prepared at different gelation concentration (c₀). The Young’s modulus (E) for the gel with low c₀ was greater than that for the gel with high c₀. Significant difference also appeared in the stress relaxation behavior: the gel with low c₀ showed greater and slower stress reduction. The results were explained by the specific network structure of κ-carrageenan hydrogels, where the crosslinks are composed of aggregates of κ-carrageenan chains. It was proposed that a great number of small crosslinks are generated at low c₀ including imperfect fragile crosslinks and that the weak crosslink domains disappear accompanying the uniaxial stretching of the gel. It seemed that the dissociation occurs successively under the tensile stress and contributes to the stress relaxation.