Determining molecular weight distributions from viscosity versus shear rate flow curves

1991 ◽  
Vol 31 (20) ◽  
pp. 1496-1507 ◽  
Author(s):  
William H. Tuminello ◽  
N. Cudré-Mauroux
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Flow Curves ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Processing of EPDM Polymers as Related to Structure and Rheology

1990 ◽  
Vol 63 (4) ◽  
pp. 540-553 ◽  
Author(s):  
Kenneth P. Beardsley ◽  
Richard W. Tomlinson
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Carbon Black ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Lower Shear ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Abstract We have shown that the rate of mixing oil and carbon black with EPDM polymers having the same Mooney viscosity is dependent on their molecular-weight distribution and degree of branching. Samples having broad molecular-weight distributions mix more slowly than samples with more narrow distributions, and branched samples mix more slowly than corresponding linear samples. The slower mixing of samples that are branched or broad in molecular-weight distribution is a consequence of their more elastic character. These samples tend to be more non-Newtonian in their flow characteristics and thus have high viscosities at low shear rate and low viscosities at high shear rate. They also drop more in viscosity on mixing with oil. These factors cause these polymers to wet the carbon black more slowly and to have lower shear stresses during the mixing, leading to slower mixing.

The Use of Novel F-RAFT Agents in High Temperature and High Pressure Ethene Polymerization: Can Control be Achieved?

2007 ◽  
Vol 60 (10) ◽  
pp. 788 ◽  
Author(s):  
Markus Busch ◽  
Marion Roth ◽  
Martina H. Stenzel ◽  
Thomas P. Davis ◽  
Christopher Barner-Kowollik
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
High Temperature ◽  
Degree Of Polymerization ◽  
Molecular Weight Distributions ◽  
High Pressure High Temperature ◽  
Reversible Addition ◽  
Weight Distributions ◽  
Raft Agent ◽  
Initial Results

Simulations are employed to establish the feasibility of achieving controlled/living ethene polymerizations. Such simulations indicate that reversible addition–fragmentation chain transfer (RAFT) agents carrying a fluorine Z group may be suitable to establish control in high-pressure high-temperature ethene polymerizations. Based on these simulations, specific fluorine (F-RAFT) agents have been designed and tested. The initial results are promising and indicate that it may indeed be possible to achieve molecular weight distributions with a polydispersity being significantly lower than that observed in the conventional free radical process. In our initial trials presented here (using the F-RAFT agent isopropylfluorodithioformate), a correlation between the degree of polymerization and conversion can indeed be observed. Both the lowered polydispersity and the linear correlation between molecular weight and conversion indicate that control may in principle be possible.

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