EXPERIMENTAL-OBSERVATION OF THE MOLECULAR-WEIGHT DEPENDENCE OF THE CRITICAL EXPONENTS FOR THE RHEOLOGY NEAR THE GEL POINT

Linear viscoelasticity experiments are shown to follow a regular patte rn near the gel point of chemical and physical gels. Experimental obse rvations are reviewed for the three critical exponents of rheology: th e relaxation exponent (n) for the material directly at the gel point, the critical exponent (alpha) of the divergence of the longest relaxat ion time in the approach of the gel point, and the exponent (kappa) fo r the rate of change of the spectrum at the transition. The molecular weight of the precursor is an important parameter which has been studi ed recently. Other parameters are addition of diluent (solvent), off-b alancing of stoichiometry, and bulkiness of crosslinking points.