On the Use of a Kolsky Torsion Bar to Study the Transient Large-Strain Response of Polymer Melts at High Shear Rates

2004 ◽  
Vol 71 (4) ◽  
pp. 441-449 ◽  
Author(s):  
Y. Hu ◽  
R. Feng
Keyword(s):  
Polymer Melts ◽  
Large Strain ◽  
High Rate ◽  
Low Density Polyethylene ◽  
Large Strains ◽  
Low Density ◽  
Strain Response ◽  
High Shear ◽  
Instantaneous Rate ◽  
Torsion Bar

A Kolsky torsion bar is utilized successfully in a novel rheometric experiment for measuring the transient large-strain response of polymer melts under high shear-rate loading. A molten low-density polyethylene is studied with the new technique. The results show that the high-rate shear response of the material has an instantaneous rate dependence that may not be discernible at low rates and a strain-dependent hardening that saturates at large strains instead of fading. The usefulness of the technique and the significance of the findings are discussed in comparison with a modified rubberlike liquid theory and high-rate capillary measurements for low-density polyethylene melts.

Pulverization of Low Density Polyethylene and Rubber Under High Shear and Normal Forces

1997 ◽  
Vol 15 (2) ◽  
pp. 113-113
Author(s):  
H. Arastoopour ◽  
B. Bemstain ◽  
A. Riahi ◽  
D. Schocke
Keyword(s):  
Low Density Polyethylene ◽  
Low Density ◽  
High Shear ◽  
Normal Forces

Molecular Drag-Strain Coupling in Branched Polymer Melts

2000 ◽  
Vol 629 ◽  
Author(s):  
Richard J. Blackwell ◽  
Tom C. B. McLeish ◽  
Oliver G. Harlen
Keyword(s):  
Branch Point ◽  
Polymer Melts ◽  
Uniaxial Extension ◽  
Extensional Viscosity ◽  
Low Density Polyethylene ◽  
Model Parameters ◽  
Low Density ◽  
Branch Points ◽  
Nonlinear Rheology ◽  
Branched Polymer

ABSTRACTThe “pom-pom” model of McLeish and Larson (J. Rheol. 42, 81, 1998) provides a simple molecular theory for the nonlinear rheology of long chain branched polymer melts. The Edwards-de Gennes tube concept is used to derive a constitutive equation for a simple branched molecule composed of two star polymers linked by a single backbone chain. A feature of this model is that the backbone section of tube can stretch up to maximum length given by the maximum entropic drag-force from the arms, after which the star arms are withdrawn into the backbone tube. This produces a sharp transition in the extensional viscosity at this maximum stretch. This unphysical feature results from an over-simplification of the behaviour near the branch points.In this paper we introduce a simple treatment of the coupling between relaxed and unrelaxed polymer segments at branch-points. This allows for localised displacements of branch-point within a quadratic potential before maximum extension is reached. Displacing the branch-point reduces the length of arm outside the tube and so reduces in the drag on the star arms. This smoothes out the sharp transitions in extensional viscosity in the original “pom-pom” model at the cost of introducing an extra unknown parameter.This modification improves the prediction of the nonlinear rheology of H-polymers whose molecular structure is known. Alternatively, for polymers of unknown structure such as commercial Low Density Polyethylene, the model parameters may be fitted from linear viscoelastic and uniaxial extension data, to provide predictions for the behaviour in transient nonlinear shear and planar extension. By including local branch-point displacement we find improved agreement with the data for Low-Density Polyethylene.

PULVERIZATION OF LOW DENSITY POLYETHYLENE UNDER HIGH SHEAR AND COMPRESSION

1999 ◽  
Vol 17 (1-2) ◽  
pp. 29-41 ◽  
Author(s):  
A. RIAHI ◽  
B. BERNSTEIN ◽  
H. ARASTOOPOUR
Keyword(s):  
Low Density Polyethylene ◽  
Low Density ◽  
High Shear

Equibiaxial Extension of Two Polymer Melts: Polystyrene and Low Density Polyethylene

1985 ◽  
Vol 29 (5) ◽  
pp. 493-517 ◽  
Author(s):  
Paul R. Soskey ◽  
H. Henning Winter
Keyword(s):  
Polymer Melts ◽  
Low Density Polyethylene ◽  
Low Density

Improved Storage Stability of LDPE/SBS Blends Modified Asphalts

2002 ◽  
Vol 10 (3) ◽  
pp. 229-236 ◽  
Author(s):  
Guangtao Gao ◽  
Yong Zhang ◽  
Yinxi Zhang ◽  
Kang Sun ◽  
Yongzhong Fan
Keyword(s):  
High Temperature ◽  
Storage Stability ◽  
Optical Microscope ◽  
Low Density Polyethylene ◽  
Low Density ◽  
High Shear ◽  
High Shear Stress ◽  
Styrene Butadiene Styrene ◽  
Styrene Butadiene ◽  
Butadiene Styrene

In this paper, Low Density Polyethylene (LDPE) / Styrene-Butadiene-Styrene (SBS) blends prepared under high shear stress were used as asphalt modifiers. Compared to the asphalts modified by LDPE and SBS added directly, the blend modified asphalts showed much better storage stability in the presence of sulfur at high temperature. No visible phase separation was observed under an optical microscope at high temperature and the morphology analysis indicated that the phase structure of the LDPE/SBS blend modified asphalts was unchanged with time at high temperature. After storage at 163°Ê for 48h, the LDPE/SBS blend modified asphalts had no evidence of coalescence of polymer particles. The rheological properties of the asphalts were also improved by the addition of polymers in all cases.

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