Thermodynamically induced shear degradation

1988 ◽  
pp. 1-31 ◽  
Author(s):  
M. Ballauff ◽  
B. A. Wolf
Keyword(s):  
Shear Degradation

Shear degradation resistance of star poly(ethyleneimine) - polyacrylamides during elongational flow

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Ming Duan ◽  
Shenwen Fang ◽  
Liehui Zhang ◽  
Fuxiao Wang ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Shear Rate ◽  
Aqueous Solutions ◽  
Relative Viscosity ◽  
Reduction Rate ◽  
Elongational Flow ◽  
Exponential Dependence ◽  
Distilled Water ◽  
Shear Stability ◽  
Low Viscosity ◽  
Shear Degradation

AbstractAn experimental study of the flow-induced scission behaviour of four star hydrolyzed polyacrylamides (HPMA) with different arms during planar elongational flow in a cross-slot flow cell is described. The results showed that the shear stability of linear HPAM in distilled water was not essentially different from star HPAM. Polymer scission was not observed in either system in a shear rate range from 20,000 to 100,000s-1, which can be attributed to the strong polyelectrolyte behaviour of HPAM in distilled water. However, at the same shear rate, the star HPAMs exhibited superior shear stability in comparison to the linear HPAMs in aqueous solutions containing NaCl (CNaCl=0.2-1.0%wt) and, in particular, the initial reduction rate of relative viscosity (R) decreased with the degree of branching of the HPAMs. In addition, it was found that the R of five HPAMs in NaCl aqueous solutions exhibited an exponential dependence on shear rate, in which the coefficient C1 can be used to quantitatively evaluate shear stability. In star HPAM NaCl aqueous solutions, the increase of R with shear rate is very likely due to the decrease of the hydrodynamic radius (Rh) of these HPAMs, while the increase of R with NaCl concentrations can be attributed to the relatively low viscosity of these polymers at high NaCl concentrations.

Shear Degradation of Deoxyribonucleic Acid1

1959 ◽  
Vol 81 (19) ◽  
pp. 5136-5139 ◽  
Author(s):  
Liebe F. Cavalieri ◽  
Barbara H. Rosenberg
Keyword(s):  
Shear Degradation

Anomalous Flow of Polyisobutylene

1967 ◽  
Vol 40 (5) ◽  
pp. 1492-1504
Author(s):  
J. Kenneth Lund
Keyword(s):  
Polymer Melt ◽  
Activation Energies ◽  
The Other ◽  
Rotating Flow ◽  
Viscosity Data ◽  
Flow Units ◽  
Uniform Shear ◽  
Shear Degradation ◽  
New Type ◽  
Flow Activation

Abstract This work began as a study of shear degradation in a polymer melt subjected to a uniform shear field. A new type of biconical rotor rheometer was designed and constructed for it. Early in the investigation, however, phenomena were observed which led our efforts away from the original objectives. Viscosity data on a polyisobutylene melt have been obtained which indicate the presence of two flow regions, having significantly different flow activation energies. Normal entanglement flow is encountered in one, the other is apparently dominated by a different mechanism, which results in lower flow activation energies. A mechanism involving rotating flow units is proposed and applied to describe this region.

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