Concentration dependence of mechanical properties of gelatin near the sol-gel transition point

The concentration dependence of mechanical properties for gelatin near the sol–gel transition point was analyzed by the scaling law derived from the percolation theory, and compared with the results previously obtained for polyacrylamide. The critical concentration at the sol–gel transition point, ϕ_g, was estimated from the concentration (ϕ) vs. the reciprocal of viscosity (η) plots by extrapolating 1/η to zero. The critical exponent for sol viscosity, s, was estimated from the slope of a log(ϕ_g–ϕ) vs. log η plot. The critical exponent s was about 1.1, being larger than the value predicted by the percolation theory assuming the superconductor model. The critical exponent for gel elasticity, t, was estimated from the slope of a log(ϕ–ϕ_g) vs. log G′ plot, where G′ is the dynamic shear modulus at a frequency of 2Hz. The critical exponent t was about 2, being similar to the value predicted by the percolation theory.