A constitutive analysis of the extensional flows of nearly monodisperse polyisoprene melts

• Published in: Polymer (Guilford) 2016-11, Vol.104, p.251-257
• Main Author: Rasmussen, Henrik Koblitz
• Format: Article
• Language: English
• Subjects: Adiabatic; Adiabatic flow; Entanglement; Extensional flows; Formulations; Interchain pressure; Macromolecules; Melts; Molecular weight; Molecular weight distribution; Polyisoprene melt; Polyisoprenes; Polymer rheology; Polymers; Pressure; Relaxation time; Rheological properties; Rheology; Shear flow; Stress functions; Studies; Viscosity; Viscosity measurement
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2016.05.019

Here two particular formulations [M.H. Wagner, S. Kheirandish, O. Hassager, Journal of Rheology 49 (6) (2005) 1317–1327; H.K. Rasmussen, Q. Huang, Rheologica Acta 53 (3) (2014) 199–208; G. Marrucci, G. Ianniruberto, Macromolecules 37 (10) (2004) 3934–3942] of the ‘interchain pressure’ [39], incorporated into the molecular stress function method [M.H. Wagner, S. Kheirandish, O. Hassager, Journal of Rheology 49 (6) (2005) 1317–1327], are used to assess the extensional [J.K. Nielsen, O. Hassager, H.K Rasmussen, G.H. McKinley, Journal of Rheology 53 (6) (2009) 1327–1346; G. Liu, H. Sun, S. Rangou, K. Ntetsikas, A. Avgeropoulos, S.-Q. Wang, Journal of Rheology 57 (1) (2013) 89–104] and shear viscosities [D. Auhl, J. Ramirez, A.E. Likhtman, P. Chambon, C. Fernyhough, Journal of Rheology 52 (3) (2008) 801–835] of narrow molecular weight distributed (NMMD) polyisoprene melts. These two formulations are expected to represent the highest [M.H. Wagner, S. Kheirandish, O. Hassager, Journal of Rheology 49 (6) (2005) 1317–1327, G. Marrucci, G. Ianniruberto, Macromolecules 37 (10) (2004) 3934–3942] and lowest level [H.K. Rasmussen, Q. Huang, Rheologica Acta 53 (3) (2014) 199–208] of the ‘interchain pressure’. The needed Rouse times are here defined as τR/τmax ∝ (M/Me)−1.4 with a proportional factor of 1.4, achieved based on the viscosity measurement. τmax is the maximal relaxation time, M the molecular weight and the entanglement molecular weight Me=(4/5)ρRT/GN0 [M. Doi M, S.F. Edwards, The Theory of Polymer Dynamics; Clarendon Press: Oxford (1986)]. ρ is the density, R the gas constant, T the temperature and GN0  the plateau modulus. The method by [M.H. Wagner, S. Kheirandish, O. Hassager, Journal of Rheology 49 (6) (2005) 1317–1327, G. Marrucci, G. Ianniruberto, Macromolecules 37 (10) (2004) 3934–3942] predicts start-up of extensional viscosities significantly below the measured value. The formulations by [H.K. Rasmussen, Q. Huang, Rheologica Acta 53 (3) (2014) 199–208] seem to be in agreement with both the start-up of extension as well as the shear flow of all NMMD polyisoprenes. Potential non-isothermal effects were addressed computationally using the pseudo time principle, assuming the most critical case of adiabatic heating. [Display omitted] •The constant interchain pressure idea predicts the flow of monodisperse polyisoprenes.•Agreement with startup of extension viscosity of nearly monodisperse polyisoprenes.•Agreement with startup and steady shear viscosity of n