Investigation of Elastic Modulus of Xanthan and Locust Bean Gum at Different Concentrations of Mixture Using Cascade Model

Abstract

Small amplitude oscillatory shear tests were performed to measure the elastic modulus of 1:1 xanthan–locust bean gum (X/L) mixed gels prepared with different total polymer concentrations (C = 0.1% to 3%). The critical concentration of X/L mixture was determined to be 0.15%. Based on the elasticity exponent (t) values, the concentration–modulus power–law relationship suggested the existence of two concentration regimes – a low concentration regime (0.15 ≤ C ≤ 0.5%) with tlow = 3.88 and a high concentration regime (0.5 ≤ C ≤ 3.0%) with thigh = 1.47. The elastic active network chain of X/L mixed gels was determined by the cascade model, and compared with the similar calculation based on the classical rubber elastic theory. The cascade model clearly showed the existence of nonideality parameter and enthalpic contribution to the X/L mixed gel. Practical applications The concentration dependence at the highest interaction might be useful for developing highly concentrated xanthan and locust bean gum mixture gels. Most studies of xanthan and locust bean gum mixtures focused only on the lower concentration regime. In this study the modulus at a higher concentration increased but eventually saturated.