Viscous and elastic stresses in extensional rheometry

摘要: Abstract The steady and transient stress data of Orr Sridhar (Journal Non-Newtonian Fluid Mechanics, 67 (1996) 77–103) for fluid A B in uniaxial extension is compared with growth relaxation predicted using the FENE-CR model. It shown that a rapid initial following extension, which resembles Sridhar, by model due to increasing stiffness nonlinear spring chain extension. further magnitude decrease depends approximately linearly on rate strain if analysis procedure applied results model, an apparent viscous contribution obtained from purely elastic Finally, found be similar experimentally. therefore concluded experiments most likely primarily dependence stresses end-to-end length polymer contributions are much smaller than suggested. Since polyisobutylenes fluids polydisperse, multi mode models intended mimic effects molecular weight distribution also considered. increase at short times, but slow down long times. conjectured polydispersity may responsible retraction polymers observed