Now showing items 1-20 of 30

    • Bubble Growth From First Principles 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Wu, Xianghong; Kolitawong, Chanyut; Aumnate, Chuanchom; Mix, Adam W. (2016-07-05)
      We consider the simplest relevant problem in the foaming of molten plastics, the growth of a single bubble in a sea of highly viscous Newtonian fluid, and without interference from other bubbles. This simplest problem has ...
    • Chain Extended Poly(3—hydroxybutyrate) With Improved Rheological Properties and Thermal Stability, Through Reactive Modification in the Melt State 

      Kolahchi, Ahmad Rezaei; Kontopoulou, Marianna (2015-10-04)
      Branching and crosslinking of polyhydroxybutyrate (PHB) is accomplished for the first time through reactive modification in the melt state, using dicumyl peroxide (DCP) as the free-radical initiator and a tri-functional ...
    • Complex Polymer Orientation 

      Gilbert, Peter H. (2015-07)
      Previously, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory shear (LAOS) flow. We derived the expression for the polymer orientation ...
    • Die Drool and Polymer Degradation 

      Hoy, Geoffrey S.; Giacomin, A. Jeffrey; Gilbert, Peter H. (2015-06-24)
      Die drool is an operational problem associated with polymer extrusion. Extrudate collects outside of the die, necessitating periodic disruptions for cleaning. There exists some debate as to the mechanism that produces ...
    • Elastomers in Large-Amplitude Oscillatory Uniaxial Extension Revisited 

      Dessi, Claudia; Vlassopoulos, Dimitris; Giacomin, A. Jeffrey; Saengow, Chaimongkol (2017-07)
      In this work, we subject elastomers to a fixed pre-stretch in uniaxial extension, ε p , upon which a large-amplitude, ε 0 , oscillatory uniaxial extensional (LAOE) deformation is superposed. We find that if both ε p and ε ...
    • Elastomers in Oscillatory Uniaxial Extension 

      Dessi, Claudia; Vlassopoulos, Dimitris; Giacomin, A. Jeffrey; Saengow, Chaimongkol (2016-02)
      In this work, we subject elastomers to a fixed pre-stretch in uniaxial extension, ε p , upon which a large-amplitude, ε 0 , oscillatory uniaxial extensional (LAOE) deformation is superposed. We find that if both ε p and ε ...
    • Exact Analytical Solution for Large-Amplitude Oscillatory Shear Flow 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut (2015-03-16)
      When polymeric liquids undergo large-amplitude shearing oscillations, the shear stress responds as a Fourier series, the higher harmonics of which are caused by fluid nonlinearity. Previous work on large-amplitude oscillatory ...
    • Exact Analytical Solution for Large-Amplitude Oscillatory Shear Flow from Oldroyd 8-Constant Framework: Shear Stress 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut (2017-01)
      The Oldroyd 8-constant model is a continuum framework containing, as special cases, many important constitutive equations for elastic liquids. When polymeric liquids undergo large-amplitude oscillatory shear flow, the shear ...
    • Exact-solution for Cone-plate Viscometry 

      Giacomin, A. Jeffrey; Gilbert, Peter H. (2017-08)
      The viscosity of a Newtonian fluid is often measured by confining the fluid to the gap between a rotating cone that is perpendicular to a fixed disk. We call this experiment cone-plate viscometry. When the cone angle ...
    • Extruding Plastic Pipe From Eccentric Dies 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut (2015-05-25)
      To solidify plastic pipe, the pipe is transported through a long cooling chamber. Inside this chamber, inside the pipe, the plastic remains molten, and this inner surface solidifies last. The flow due to the self-weight ...
    • Fluid Elasticity in Plastic Pipe Extrusion: Loads on Die Barrel 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey (2017-07)
      In large thick plastic pipe extrusion, the residence in the cooling chamber is long, and the melt inside the pipe sags under its own weight, causing the product to thicken on the bottom (and to thin on the top). To compensate ...
    • Fourier Decomposition of Polymer Orientation in Large-Amplitude Oscillatory Shear Flow 

      Giacomin, A. Jeffrey; Gilbert, Peter H.; Schmalzer, Andrew M. (2015-03-17)
      In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory shear flow, a flow experiment that has gained a significant following ...
    • Knuckle Formation From Melt Elasticity in Plastic Pipe Extrusion 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut (2016-07)
      When plastic pipe is solidified, it proceeds through a long cooling chamber. Inside the chamber, inside the extrudate, the plastic is molten, and this inner surface solidifies last. Sag then happens inside this cooling ...
    • Large-Amplitude Oscillatory Shear: Comparing Parallel-Disk with Cone-Plate Flow 

      Giacomin, A. Jeffrey; Gilbert, Peter H.; Merger, Dimitri; Wilhelm, Manfred (2014-09-30)
      We compare the ratio of the amplitudes of the third to the first harmonic of the torque, |T3|/|T1|, measured in rotational parallel-disk flow, with the ratio of the corresponding harmonics of the shear stress, |T3|/|T1|, ...
    • Macromolecular Origins of Fifth Shear-Stress Harmonic in Large-Amplitude Oscillatory Shear Flow 

      Jbara, Layal M.; Gilbert, Peter H.; Giacomin, A. Jeffrey (2016-08)
      This study examines the simplest relevant molecular model of a polymeric liquid in large-amplitude oscillatory shear (LAOS) flow: the suspension of rigid dumbbells in a Newtonian solvent. For such suspensions, the viscoelastic ...
    • Molecular Origins of Higher Harmonics in Large-Amplitude Oscillatory Shear Flow: Shear Stress Response 

      Gilbert, Peter H.; Giacomin, A. Jeffrey (2016-11-01)
      Recent work has focused on deepening our understanding of the molecular origins of the higher harmonics that arise in the shear stress response of polymeric liquids in large-amplitude oscillatory shear flow. For instance, ...
    • Normal Stress Differences from Oldroyd 8-Constant Framework: Exact Analytical Solution for Large-Amplitude Oscillatory Shear Flow 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey (2017-03)
      The Oldroyd 8-constant framework for continuum constitutive theory contains a rich diversity of popular special cases for polymeric liquids. In this paper, we use part of our exact solution for shear stress to arrive at ...
    • Normal Stress Differences in Large-Amplitude Oscillatory Shear Flow for Dilute Rigid Dumbbell Suspensions 

      Schmalzer, Andrew M.; Bird, R. Byron; Giacomin, A. Jeffrey (2014-08-25)
      We examine the simplest relevant molecular model for large-amplitude oscillatory shear (LAOS) flow of a polymeric liquid: the suspension of rigid dumbbells in a Newtonian solvent. We find explicit analytical expressions ...
    • Orientation in Large-Amplitude Oscillatory Shear 

      Schmalzer, Andrew M.; Giacomin, A. Jeffrey (2014-09-30)
      We examine the simplest relevant molecular model for large-amplitude oscillatory shear flow of a polymeric liquid: the dilute suspension of rigid dumbbells in a Newtonian solvent. We find explicit analytical expressions ...
    • Padé Approximants for Large-Amplitude Oscillatory Shear Flow 

      Giacomin, A. Jeffrey; Saengow, Chaimongkol; Guay, Martin; Kolitawong, Chanyut (2015-03-17)
      Analytical solutions for either the shear stress or the normal stress differences in large-amplitude oscillatory shear flow, both for continuum or molecular models, often take the form of the first few terms of a power ...