Dependence of linear viscoelastic critical strain and stress values on extent of gelation for a thermally activated gelling system

A large body of literature is focused on the accurate determination of a ge l point for systems undergoing a sol-gel phase transition. Investigation in to the limiting strain and stress for linear viscoelastic behaviour at vari ous stages of a phase transition such as gelation is a subject that is rare ly commented on. The small amplitude oscillatory rheological behaviour of a biopolymer cross-linker system through a thermally activated sol-gel trans ition is presented. Mechanical spectra were interpreted through application of the gelation criteria of Chambon and Winter (Winter and Chambon 1986, C hambon and Winter 1987), where the (so-called gel strength) parameter S, an d relaxation exponent, n are obtained. A detailed study of the limit of lin ear viscoelasticity yields important trends in critical stress (sigma (o)(c )) and critical strain (gamma (o)(c)) limits highlighting the possible expe rimental difficulties associated with mechanical measurements obtained in c lose proximity to the gel point.