Prediction of linear viscoelastic response for entangled polyolefin melts from molecular weight distribution

1996 ◽  
Vol 36 (6) ◽  
pp. 852-861 ◽  
Author(s):  
Scott H. Wasserman ◽  
William W. Graessley
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Viscoelastic Response ◽  
Linear Viscoelastic

Viscoelastic Characterization of Long Branching and Gel in Butadiene-Acrylonitrile Copolymer Elastomers

1980 ◽  
Vol 53 (1) ◽  
pp. 14-26 ◽  
Author(s):  
N. Nakajima ◽  
E. R. Harrell
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
General Rule ◽  
The Other ◽  
Model Systems ◽  
Newtonian Flow ◽  
Long Chain Branching ◽  
Linear Viscoelastic ◽  
Definition Of

Abstract Difficulties in relating long-chain branching to processability may be attributable to two causes: one is the definition, pertinent to processability, of what long branches are and the other is a method of determining long branching which is free from interference by other material variables, such as molecular weight distribution, gel, and “short” branches. Measurements of the dilute solution properties are tedious, time-consuming, and require skill for precision. In addition, the requirement for filtering the solution practically obliterates the result, regardless of how precise the measurement may be, because elastomers, as a general rule, have or are suspected to have an insoluble gel fraction. Recent advances in viscoelastic studies of model polymers show that the branches must be 2–3 times longer than the “entanglement coupling” distance in order to exhibit enhancement of viscosity in the Newtonian flow. Whereas Newtonian flow provides a precise definition of the long branches, it is not accessible for most of the elastomers. In the observed time scale, the linear viscoelastic properties as well as the steady-state viscosities are affected not only by branches but also by gels and molecular weight distribution. When these material variables are changed one at a time in the properly designed model systems, their effects are separately observable. On the other hand with a sample of unknown background, the effect of long branching is usually inseparable from those of other variables.

Effect of Viscosity Stabilizer on the Properties and Structure of Raw Constant Viscosity Rubber

2012 ◽  
Vol 557-559 ◽  
pp. 947-951
Author(s):  
Yong Zhou Wang ◽  
Ping Yue Wang ◽  
Bei Long Zhang ◽  
Hong Hai Huang ◽  
Li Ding ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Low Frequency ◽  
Hydroxylamine Hydrochloride ◽  
Dynamic Mechanical Properties ◽  
Linear Viscoelastic ◽  
Strain Sweep ◽  
Constant Viscosity

The properties of raw constant viscosity natural rubber were measured using a rubber processing analyzer. The results show that the rubber processing analyzer can characterize well the effect of viscosity stabilizer on the dynamic mechanical properties of raw constant viscosity rubber by applied strain sweep or frequency sweep. In linear viscoelastic region, the increment of the dynamic torque S’ of the constant viscosity natural rubber prepared with hydroxylamine hydrochloride decreases with the increase in the level of hydroxylamine hydrochloride . In the range of low frequency, the increment of the dynamic modulus G’ of constant viscosity natural rubber prepared with hydroxylamine hydrochloride is obvious lower than those of natural rubber and constant viscosity natural rubber prepared with aniline. G’ of the constant viscosity natural rubber prepared with aniline is just only a little higher than that of natural rubber. Hydroxylamine hydrochloride and aniline can decrease the molecular weight of rubber, and change the molecular weight distribution. The dynamical properties of constant viscosity natural rubber are dependent on the molecular weight and the molecular weight distribution.

From molecular weight distribution to linear viscoelastic properties and back again: application to some commercial high-density polyethylenes

2012 ◽  
Vol 21 (6) ◽  
pp. 403-413 ◽  
Author(s):  
Jafar Eskandari Jam ◽  
Mehdi Nekoomanesh ◽  
Mostafa Ahmadi ◽  
Hassan Arabi
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Viscoelastic Properties ◽  
High Density ◽  
Linear Viscoelastic
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