SHEAR HISTORY EFFECTS IN ASSOCIATIVE THICKENER SOLUTIONS

Rheological investigations have revealed the strong dependency of the solution properties of associative thickener solutions on their shear history. Studies involved the measurement of the apparent solution vis cosity both as a function of the shear time at constant shear rates an d as a function of shear rate. Thixotropic behavior was observed at al l copolymer concentrations studied. Furthermore, the effect of shear h istory on the viscoelasticity of the solutions was studied with stress relaxation and dynamic measurements. Results are explained in terms o f the balance between interchain and intrachain associations of the co polymer molecules in solution, and the kinetics of the molecular reorg anization and dissociation-reassociation processes.