Browsing Polymers Research Group Technical Report Series by Title
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Fluid Elasticity in Plastic Pipe Extrusion: Loads on Die Barrel
(201707)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 LargeAmplitude Oscillatory Shear Flow
(20150317)In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in largeamplitude oscillatory shear flow, a flow experiment that has gained a significant following ... 
Hydrodynamic Interaction for Rigid Dumbbell Suspensions in Steady Shear Flow
(201812)From kinetic molecular theory, we can attribute the rheological behaviors of polymeric liquids to macromolecular orientation. The simplest model to capture the orientation of macromolecules is the rigid dumbbell. For a ... 
Knuckle Formation From Melt Elasticity in Plastic Pipe Extrusion
(201607)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 ... 
LargeAmplitude Oscillatory Shear Flow Loops for LongChain Branching From General Rigid BeadRod Theory
(202004)General rigid beadrod theory [Hassager, J Chem Phys, 60, 4001 (1974)] explains polymer viscoelasticity from macromolecular orientation. By means of this theory, we relate the complex viscosity of polymeric liquids to the ... 
LargeAmplitude Oscillatory Shear: Comparing ParallelDisk with ConePlate Flow
(20140930)We compare the ratio of the amplitudes of the third to the first harmonic of the torque, T3/T1, measured in rotational paralleldisk flow, with the ratio of the corresponding harmonics of the shear stress, T3/T1, ... 
Macromolecular Origins of Fifth ShearStress Harmonic in LargeAmplitude Oscillatory Shear Flow
(201608)This study examines the simplest relevant molecular model of a polymeric liquid in largeamplitude oscillatory shear (LAOS) flow: the suspension of rigid dumbbells in a Newtonian solvent. For such suspensions, the viscoelastic ... 
Macromolecular Tumbling and Wobbling in LargeAmplitude Oscillatory Shear Flow
(201811)For a suspension of rigid dumbbells, in any simple shear flow, we recently solved for the diffusion equation for the orientation distribution function by a power series expansion in the shear rate magnitude. In this paper, ... 
Molecular Continua for Polymeric Liquids in LargeAmplitude Oscillatory Shear Flow
(201705)In this paper, we connect a molecular description of the rheology of a polymeric liquid to a continuum description, and then test this connection for largeamplitude oscillatory shear flow (LAOS). Specifically, for the ... 
Molecular Origins of Higher Harmonics in LargeAmplitude Oscillatory Shear Flow: Shear Stress Response
(20161101)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 largeamplitude oscillatory shear flow. For instance, ... 
Nonlinear Core Deflection in Injection Molding
(201802)Injection molding of thin slender parts is often complicated by core deflection. This deflection is caused by molten plastics race tracking through the slit between the core and the rigid cavity wall. The pressure of this ... 
Normal Stress Differences from Oldroyd 8Constant Framework: Exact Analytical Solution for LargeAmplitude Oscillatory Shear Flow
(201703)The Oldroyd 8constant 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 LargeAmplitude Oscillatory Shear Flow for Dilute Rigid Dumbbell Suspensions
(20140825)We examine the simplest relevant molecular model for largeamplitude oscillatory shear (LAOS) flow of a polymeric liquid: the suspension of rigid dumbbells in a Newtonian solvent. We find explicit analytical expressions ... 
Order in Oscillatory Shear Flow
(201812)We examine the second order orientation tensor for the simplest molecular model relevant to a polymeric liquid in largeamplitude oscillatory shear flow (LAOS), the rigid dumbbell suspension. For this we use an approximate ... 
Orientation Distribution Function Pattern for Rigid Dumbell Suspensions In Any Simply Shear Flow
(201809)For rigid dumbbells suspended in a Newtonian solvent, the viscoelastic response depends exclusively on the dynamics of dumbbell orientation. The orientation distribution function ψ (θ ,φ ,t) represents the probability of ... 
Orientation in LargeAmplitude Oscillatory Shear
(20140930)We examine the simplest relevant molecular model for largeamplitude oscillatory shear flow of a polymeric liquid: the dilute suspension of rigid dumbbells in a Newtonian solvent. We find explicit analytical expressions ... 
Padé Approximant for Normal Stress Differences in LargeAmplitude Oscillatory Shear Flow
(201711)Analytical solutions for the normal stress differences in largeamplitude oscillatory shear flow (LAOS), for continuum or molecular models, normally take the form of the first few terms of a series expansion in the shear ... 
Padé Approximants for LargeAmplitude Oscillatory Shear Flow
(20150317)Analytical solutions for either the shear stress or the normal stress differences in largeamplitude oscillatory shear flow, both for continuum or molecular models, often take the form of the first few terms of a power ... 
Plastic Pipe Solidification: Exact Solutions in Cylindrical Coordinates
(201512)For polymer melt solidification in plastic pipe extrusion, we perform an energy balance on the pipe extrudate in cylindrical coordinates to arrive at exact solutions for the temperature, and for the solidification rate. ... 
Polymer Branching and First Normal Stress Differences in SmallAmplitude Oscillatory Shear Flow
(201911)General rigid beadrod theory [Hassager, J Chem Phys, 60, 4001 (1974)] explains polymer viscoelasticity from macromolecular orientation. By means of general rigid beadrod theory, we relate the normal stress differences ...