Rheological Properties of Styrene-Ethylene Oxide Block Copolymers: Transition and Melt Flow Behavior

Abstract Polymers have large bulk compressibility in the molten state /1/ and their rheological properties are largely affected by pressure applied in polymer processing. The volumetric strain induced by pressure consists of instantaneous and retarded elastic strains, both of which are proportional to pressure, and recover reversibly when pressure is removed. In many crystalline polymers, as observed by B. Maxwell for polyethylene, retarded elastic strain is large, and due mostly to pressure crystallization. This paper describes results of experimental studies relating pressure effects on rheological properties of melt polymers with polymer processing and bulk properties of products. The following items are discussed: pressure induced shear stress, analysis of local deformation pattern, critical shear stress for melt flow fracture, relationship between power law index and bulk compressibility, effects of hydrostatic pressure on melt flow behavior, pressure efficiency of injection molding, jetting phenomena, shrinkage in injection moldings, residual strain, and super-high-pressure injection molding process.

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IDENTIFICATION OF RHEOLOGICAL PROPERTIES OF POLY(ETHYLENE OXIDE) – WATER SOLUTIONS

IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA ◽

10.6060/ivkkt.20206309.6236 ◽

2020 ◽

Vol 63 (9) ◽

pp. 82-87

Author(s):

Ryszard Wójtowicz ◽

Katarzyna Kocewiak ◽

Andrey A. Lipin

Keyword(s):

Ethylene Oxide ◽

Rheological Properties ◽

Flow Behavior ◽

Newtonian Fluids ◽

Shear Stresses ◽

Water Solutions ◽

Marquardt Algorithm ◽

Wide Range ◽

Poly Ethylene Oxide ◽

Poly Ethylene

In the paper results of investigations of rheological properties for selected PEO-water solutions are presented. On the basis of measurements, carried out with use of rotational viscosimeter values of shear stresses were determined in the relatively wide range of shear rates. Rheological curves were described by the Ostwald de Waele model (or so-called power-law). The model coefficients such as the fluid consistency coefficient k and the flow behavior index n were determined using Levenberg−Marquardt algorithm for nonlinear estimation. The influence of temperature on properties and behavior examined non-Newtonian fluids was also determined. Results were processed in the curve shift parameter at. Experiments shown a significant effect of poly(ethylene oxide) concentration cPEO on rheological properties of examined solutions. For the lowest concentration (cPEO=1.2%) solutions exhibited properties similar to Newtonian fluids with values of n close to 1. With increasing of PEO concentration in water (cPEO=2.4-4.8%), solutions exhibited properties as non - Newtonian fluids, pseudoplastic, without yield limit. In these cases values of n were below unity and for the highest concentration (cPEO=4.8%) belonged to the range of n=0.5694-0.7536, depending on the temperature. Results of investigations can be used during numerical simulations, design and optimization of industrial equipment, working with fluids of this kind, including mixing vessels, columns or heat exchangers.

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Mechanical and Structural Consequences of Associative Dynamic Cross-Linking in Acrylic Diblock Copolymers

10.26434/chemrxiv.10000232.v1 ◽

2019 ◽

Author(s):

Jacob Ishibashi ◽

Yan Fang ◽

Julia Kalow

Keyword(s):

Block Copolymers ◽

Rheological Properties ◽

Diblock Copolymers ◽

Cross Linking ◽

Statistical Copolymer

<p>Block copolymers are used to construct covalent adaptable networks that employ associative exchange chemistry (vitrimers). The resulting vitrimers display markedly different nanostructural, thermal and rheological properties relative to those of their statistical copolymer-derived counterparts. This study demonstrates that prepolymer sequence is a versatile strategy to modify the properties of vitrimers.</p>

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Visualization of Melt-Flow Behavior Inside the Runner in Ultra High Speed Injection Molding

International Polymer Processing ◽

10.3139/217.0997 ◽

2006 ◽

Vol 21 (5) ◽

pp. 464-472 ◽

Cited By ~ 4

Author(s):

S. Hasegawa ◽

H. Yokoi

Keyword(s):

Injection Molding ◽

High Speed ◽

Flow Behavior ◽

Melt Flow ◽

Ultra High Speed

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Influence of biopolymers on the rheological properties of seafloor sediments and the runout behavior of submarine debris flows

Scientific Reports ◽

10.1038/s41598-021-81186-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jun Kameda ◽

Hamada Yohei

Keyword(s):

Rheological Properties ◽

Debris Flows ◽

Extracellular Polymeric Substances ◽

Flow Behavior ◽

Mass Movement ◽

Rheological Parameters ◽

Natural Environments ◽

Natural Systems ◽

Chemical Conditions ◽

Seafloor Sediments

AbstractSubmarine debris flows are mass movement processes on the seafloor, and are geohazards for seafloor infrastructure such as pipelines, communication cables, and submarine structures. Understanding the generation and run-out behavior of submarine debris flows is thus critical for assessing the risk of such geohazards. The rheological properties of seafloor sediments are governed by factors including sediment composition, grain size, water content, and physico-chemical conditions. In addition, extracellular polymeric substances (EPS) generated by microorganisms can affect rheological properties in natural systems. Here we show that a small quantity of EPS (~ 0.1 wt%) can potentially increase slope stability and decrease the mobility of submarine debris flows by increasing the internal cohesion of seafloor sediment. Our experiments demonstrated that the flow behavior of sediment suspensions mixed with an analogue material of EPS (xanthan gum) can be described by a Herschel–Bulkley model, with the rheological parameters being modified progressively, but not monotonously, with increasing EPS content. Numerical modeling of debris flows demonstrated that the run-out distance markedly decreases if even 0.1 wt% of EPS is added. The addition of EPS can also enhance the resistivity of sediment to fluidization triggered by cyclic loading, by means of formation of an EPS network that binds sediment particles. These findings suggest that the presence of EPS in natural environments reduces the likelihood of submarine geohazards.

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