Role of Solvent Nature on Rheological Properties of Nylon 6,6 Solutions

The rheological properties of concentrated solutions of nylon 6,6 of various molecular weights in various solvents have been determined in steady shear flow. Four solvents including 90% formic acid, m‐cresol, 97% H2SO4, and 100% H2SO4 were selected based on their effect on the ionic nature of nylon 6,6 in dilute solutions. The magnitude of the rheological properties of concentrated solutions depended on the solvent when compared at the same shear rate (γ) and segment contact parameter (cMw, where c is the concentration and Mw is the weight average molecular weight). However, as observed by others, the critical value of cMw for the onset of entanglements was independent of the solvent. The contact parameter was effective in reducing values of η0 versus cMw to a single curve for three of the solvents but values of η0 for formic acid solutions were consistently two orders of magnitude lower than for the other solutions. Values of the equilibrium compliance, Je0, were highest for the formic acid solution...