Browsing Polymers Research Group Technical Report Series by Publish Date
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Slip Heating in Die Drool
(20140514)When molten plastic is extruded from a die, it can collect on the open die face. Called die drool, this phenomenon costs plastics manufacturers by requiring shutdown for die cleaning. This has been attributed to cohesive ... 
πάντα ῥεῖ (Everything Flows): Motto for Rheology
(20140523)This historical study deepens the rheologist’s understanding of the motto of The Society of Rheology, of its history, and of its many typographies. The motto “πάντα ῥεῖ” is not verbatim something written or said by the ... 
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 ... 
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, ... 
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 ... 
Slip Heating in Die Drool with Viscous Dissipation
(20141006)Plastics can buildup on the die lip during extrusion. This phenomenon is called die drool and can be costly for plastics producers, requiring periodic shutdowns for die cleaning. Die drool has been attributed to the ... 
Wall Slip Heating
(20150105)When molten plastic is extruded, the upper limiting throughput is often dictated by fine irregular distortions of the extrudate surface. Called sharkskin melt fracture, plastics engineers spike plastics formulations with ... 
Exact Analytical Solution for LargeAmplitude Oscillatory Shear Flow
(20150316)When polymeric liquids undergo largeamplitude shearing oscillations, the shear stress responds as a Fourier series, the higher harmonics of which are caused by fluid nonlinearity. Previous work on largeamplitude oscillatory ... 
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 ... 
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 ... 
Extruding Plastic Pipe From Eccentric Dies
(20150525)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 selfweight ... 
Die Drool and Polymer Degradation
(20150624)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 ... 
Chain Extended Poly(3—hydroxybutyrate) With Improved Rheological Properties and Thermal Stability, Through Reactive Modification in the Melt State
(20151004)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 freeradical initiator and a trifunctional ... 
Reflections on Inflections
(20151111)In plastics processing, the single most important rheological property is the steady shear viscosity curve: the logarithm of the steady shear viscosity versus the logarithm of the shear rate. This curve governs the volumetric ... 
Temperature Rise in a Verging Annular Die
(20151207)Plastic pipes, tubes or catheters are extruded by pressure‑driven flows through annular dies. Whereas die lands are straight, the section connecting the die land to the extruder either converges or diverges, converging ... 
Polymer Fluid Dynamics: Continuum and Molecular Approaches
(20160620)To solve problems in polymer fluid dynamics, one needs the equation of continuity, motion, and energy. The last two equations contain the stress tensor and the heatflux vector for the material. There are two ways to ... 
Bubble Growth From First Principles
(20160705)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 ... 
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, ... 
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 ... 
Transport Phenomena in Eccentric Cylindrical Coordinates
(201609)Studies in transport phenomena have been limited to a select few coordinate systems. Specifically, Cartesian, cylindrical, spherical, Dijksman toroidal, and bipolar cylindrical coordinates have been the primary focus of ...