caa a22 4500 605466882 CHVBK 20210128100309.0 cr unu---uuuuu 210128e20150201xx s 000 0 eng 10.1007/s00397-014-0814-y doi (NATIONALLICENCE)springer-10.1007/s00397-014-0814-y Experimental considerations on the step shear strain in polymer melts: sources of error and windows of confidence [Elektronische Daten] [Huagui Zhang, Khalid Lamnawar, Abderrahim Maazouz, João Maia] Shear step strain experiments with various strain amplitudes have been performed on poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) melts using both stress-controlled and strain-controlled rheometers. Firstly, the onset of the rheological nonlinearity, i.e., nonlinear stress damping behavior, occurring after a large step strain is found to be a phenomenological consequence of an abrupt stress decline within the transient period of strain actuation. Such a feature, analogous to the stress overshoot in a fast startup shear with sufficiently high rates, is interpreted based on theoretical frameworks concerning chain disentanglement/re-entanglement arising from chain retraction. Furthermore, this work infers that full technical considerations in step strain experiments are indispensable for acquisition of accurate stress relaxation data, as some common but easily overlooked technical problems are influential, probably introducing errors. For instance, a too long finite rise time and a stress overload enable to hinder the nonlinearity onset in the transient period, resulting in inaccurate experimental data. In this sense, the stress-controlled rheometer is advantageous relative to the strain-controlled one, although the inertia in the stress-controlled mode incurs a strain overshoot effect. Nevertheless, the amplitude-dependent strain overshoot offers a very subtle effect on the stress damping behavior. Moreover, transducer compliance problems need to be taken into account, especially for high stiffness polymers. Overall, the effects of such technical factors are dictated by their ability to influence the chain stretching/retraction and the disentanglement. A well-considered experimental methodology is necessary to achieve confidence windows in step strain experiments for analysis accuracy. Springer-Verlag Berlin Heidelberg, 2014 Step strain nationallicence Relaxation behavior nationallicence Nonlinear rheology nationallicence Transient period nationallicence Stress damping nationallicence Disentanglement/re-entanglement theory nationallicence Melt and polymer solutions nationallicence Zhang Huagui Université de Lyon, 69361, Lyon, France aut Lamnawar Khalid Université de Lyon, 69361, Lyon, France aut Maazouz Abderrahim Université de Lyon, 69361, Lyon, France aut Maia João Department of Macromolecular Science and Engineering, Case Western Reserve University, 44106-7202, Cleveland, OH, USA aut Rheologica Acta Springer Berlin Heidelberg 54/2(2015-02-01), 121-138 0035-4511 54:2<121 2015 54 397 https://doi.org/10.1007/s00397-014-0814-y text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00397-014-0814-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Zhang Huagui Université de Lyon, 69361, Lyon, France aut NATIONALLICENCE 700 1- Lamnawar Khalid Université de Lyon, 69361, Lyon, France aut NATIONALLICENCE 700 1- Maazouz Abderrahim Université de Lyon, 69361, Lyon, France aut NATIONALLICENCE 700 1- Maia João Department of Macromolecular Science and Engineering, Case Western Reserve University, 44106-7202, Cleveland, OH, USA aut NATIONALLICENCE 773 0- Rheologica Acta Springer Berlin Heidelberg 54/2(2015-02-01), 121-138 0035-4511 54:2<121 2015 54 397