Nonlinear Polymer Rheology - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Nonlinear Polymer Rheology write by Shi-Qing Wang. This book was released on 2018-01-02. Nonlinear Polymer Rheology available in PDF, EPUB and Kindle. Integrating latest research results and characterization techniques, this book helps readers understand and apply fundamental principles in nonlinear polymer rheology. The author connects the basic theoretical framework with practical polymer processing, which aids practicing scientists and engineers to go beyond the existing knowledge and explore new applications. Although it is not written as a textbook, the content can be used in an upper undergraduate and first year graduate course on polymer rheology. • Describes the emerging phenomena and associated conceptual understanding in the field of nonlinear polymer rheology • Incorporates details on latest experimental discoveries and provides new methodology for research in polymer rheology • Integrates latest research results and new characterization techniques like particle tracking velocimetric method • Focuses on the issues concerning the conceptual and phenomenological foundations for polymer rheology • Has a companion website for readers to access with videos complementing the content within several chapters
Nonlinear Rheology of Entangled Polymers
Nonlinear Rheology of Entangled Polymers - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Nonlinear Rheology of Entangled Polymers write by Prashant S. Tapadia. This book was released on 2006. Nonlinear Rheology of Entangled Polymers available in PDF, EPUB and Kindle. "A central task in polymer rheology is to search for constitutive equations that relate the flow field with the corresponding stress field in both transient and steady states. A parallel objective is to determine the state of chain conformation as a function of the flow condition. In disagreement with previous studies, our experimental data show that entangled monodisperse polymers respond differently to the applied shear strain and shear stress. In conventional shear strain rate controlled measurement, entangled polymers result in a stress plateau well known as shear thinning while a constitutive entanglement-disentanglement transition takes place when sheared in stress-controlled mode. Direct visualization of the velocity field using particle tracking velocimentry and flow birefringence reveals that entangled polymeric fluids develop a non-homogeneou flow field across the velocity gradient direction when sheared in rate-controlled mode. Lack of uniform shear deformation is observed when these fluids are subjected to large amplitude oscillatory shear at frequencies beyond overall chain relaxation rate. The combination of rheometry, rheo-optics and particle tracking velocimetry has lead to the discovery of an entanglement-disentanglement transition in shear stress mode and the presense of a shear rate gradient across sample the thickness in shear rate controlled mode. These new results may provide a reliable phenomenological basis for the future development of a realistic description of nonlinear polymer rheology."--Abstract.
Nonlinear Rheology of Long-chain Branched Polymers
Nonlinear Rheology of Long-chain Branched Polymers - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Nonlinear Rheology of Long-chain Branched Polymers write by Gengxin Liu. This book was released on 2015. Nonlinear Rheology of Long-chain Branched Polymers available in PDF, EPUB and Kindle. Entangled polymers show significant nonlinear rheological behaviors. Those studies on the mechanical behaviors of polymer melts and solutions not only promote our understanding on polymer dynamics, but also guide the application of polymers and establish principals to design polymeric materials. Recently emerged interpretations on nonlinear rheology of linear polymers proposed by Dr. Shi-Qing Wang emphasize the network nature of entangled polymers. This dissertation studies the nonlinear rheology of long-chain branched (LCB) polymers. A new synthetic method is developed and implemented to overcome the limitation of previous methods for not being able to synthesize long enough branches. This method can produce ultra-high molecular weight LCB polymers with branches of identical length and uniform spacing between branch points. Polymers with multiple long branches show remarkable resistance to the elastic-driven decohesion comparing to linear polymers. In startup uniaxial extension, they are extraordinarily more stretchable. An empirical rule shows that the failure of entangled network, as characterized by the overshoot of engineering stress, is proportional to the square root of number of entanglements. Polymers with LCB are also more resistant to failure in stepwise extension (withstand a larger stretching ratio), which would be part of film blowing process. Historically, strain hardening stands for the upward deviation of transient extensional viscosity comparing to zero-rate transient viscosity, which typically shows up on branched polymers. Under the newly emerged conceptual framework, such behavior is due to three factors: firstly, the shrinking cross-section area leads to a factor of extension ratio in calculating true stress and transient extensional viscosity; secondly, the introduction of branches suppresses the breakdown of entangled network; lastly, the entanglement network is strengthened at sufficient high Hencky rates during extension. Entangled polymeric liquids have so far only shown strain softening upon startup shear, signified by stress overshoot. However, solutions of polystyrenes with LCB exhibit strain hardening upon startup shear at high shear rates, undergoing non-Gaussian chain stretching and reaching finite extensibility limit. The stronger than linear increase of the shear stress ends with a sharp decline, forming a cusp. At intermediate shear rates, stress overshoots always occur at the same strain, which is explained also by the length of backbone. The LCB polymers show a rich variety of transient responses to startup shear at different rates and open a large window of dynamics to meet practical applications.
Investigation of Non-linear Rheological Behaviors of Entangled Polymer Melts in Complex Geometries
Investigation of Non-linear Rheological Behaviors of Entangled Polymer Melts in Complex Geometries - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Investigation of Non-linear Rheological Behaviors of Entangled Polymer Melts in Complex Geometries write by Xiangyang Zhu. This book was released on 2012. Investigation of Non-linear Rheological Behaviors of Entangled Polymer Melts in Complex Geometries available in PDF, EPUB and Kindle. Nonlinear rheology of polymer melts has been of central interest in polymer science and engineering for the last four decades. Recent particle-tracking velocimetric (PTV) observations have revealed strain localization either during startup shear, beyond the stress overshoot, or after stepwise shear of entangled solutions and melts. Strain localization under rate-controlled shear shows that yielding, i.e., transition from elastic deformation to flow, has taken place. Under controlled stress, i.e. creep, entangled polymers also exhibit breakdown of the entanglement network in the form of an entanglement-disentanglement transition (EDT). Characterization of structural changes during creep has been performed for entangled polymer solutions undergoing EDT. The PTV method was employed to probe yielding and strain localization under large, fast external deformation of polymeric melts in uniaxial extension and capillary extrusion. Shear yielding through chain disentanglement is anticipated despite the fact that these two modes of deformation are not simple shear. During uniaxial extension, we are able to identify different failure modes of tensile decohesion and necking failure initiated by shear yielding. During capillary extrusion, entry pressure loss due to shear yielding also has been systematically studied in the fast flow region. Through Bagley extrapolation or flow curves obtained in a Couette device, the magnitude of pressure loss was determined. It was found to be proportional to one third power of the volumetric flow rate.
Nonlinear Rheology of Entangled Symmetric and Asymmetric Star Polymers
Nonlinear Rheology of Entangled Symmetric and Asymmetric Star Polymers - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Nonlinear Rheology of Entangled Symmetric and Asymmetric Star Polymers write by Amy Kathleen Tezel. This book was released on 2005. Nonlinear Rheology of Entangled Symmetric and Asymmetric Star Polymers available in PDF, EPUB and Kindle. Asymmetric stars are intriguing because they are very similar to both linear chains and symmetric stars. Currently work is being done in other groups to quantitatively describe asymmetric stars in the linear viscoelastic regime. We have synthesized our own batch of asymmetric stars and have conducted the first study of asymmetric stars in the nonlinear regime. These results are examined in the context of previous work done on linear and symmetric star polymers.
