The relaxation time of entangled HPAM solutions in flow

It is generally understood that for entangled viscoelastic polymer solutions entanglement effects are significantly weakened under strong flow. In recent years, it has been observed that, despite quiescently being entangled at use concentrations, high molecular weight HPAM solutions are characterised by their Rouse time when tran-sitioning to elastic turbulence in porous flow. Whereas this has been inferred, for these practically important solution polymers direct measurement of the apparent characteristic relaxation time under shear has not been reported. Here we use controlled-stress parallel-superposition background shear to assess the apparent charac-teristic relaxation time as a function of shear rate. Our results coincide with a recently reported calculation using Rolie-poly and Rolie-double-poly models.