UNIAXIAL COMPRESSION AND STRESS RELAXATION TESTS ON ALGINATE GELS

Abstract

ABSTRACT The rheological behavior of alginate gels was analyzed using uniaxial compression and stress relaxation tests. The engineering compressive stress (σ E )‐deformation (ɛ E curves were found to be concave upward and independent of the crosshead speed (V t for V t ≥ 120 mm/min. By considering all the stress (σ E )‐time (t) data for t greater than 10 times the average loading period, the viscoelastic response of these gels was described by means of a 3‐element Maxwell body characterized by a relaxation time of 300 s. Such gels exhibited an apparent linear viscoelastic solid behavior for ɛ E ≤ 8% and a nonlinear one for larger deformations. However, for ɛ E >32% their solid viscoelastic behavior tended to a liquid one. Empirical models allowed the viscoelastic properties, as well permanent deformation, of these gels to be quantitatively described as functions of the deformation applied and/or loading rate.