Molecular weight distributions from linear viscoelastic measurements

1996 ◽  
Vol 35 (4) ◽  
pp. 356-363 ◽  
Author(s):  
Devulapalli H. S. Ramkumar ◽  
John M. Wiest
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Linear Viscoelastic

scholarly journals Use of Linear Viscoelastic Functions to Estimate the Aging Resistance and Internal Structure of Bituminous Binders

2021 ◽  
Vol 11 (16) ◽  
pp. 7483
Author(s):  
Miriam Cappello ◽  
Giovanni Polacco ◽  
Julien Crépier ◽  
Yvong Hung ◽  
Sara Filippi
Keyword(s):  
Molecular Weight ◽  
Apparent Molecular Weight ◽  
Operating Conditions ◽  
Master Curves ◽  
Deconvolution Analysis ◽  
Molecular Weight Distributions ◽  
Wide Range ◽  
Weight Distributions ◽  
Linear Viscoelastic ◽  
Bituminous Binders

Rheology is the most widely used technique to evaluate the performance and aging of bituminous binders. Since there are many available rheological tests, there is also a wide range of aging indexes and it is not easy to choose the most appropriate one, because a single value may hardly be adequate for different properties or operating conditions. In order to generalize the usefulness of an index, a good starting point is deriving it from a set of data, such as the master curves of linear viscoelastic functions. Then, the problem is the quantification of aging in a single numerical value from continuous curves, covering a wide range of frequencies/temperatures. In this work, a summary of the aging indexes derived from the master curves is reported and discussed. The indexes are applied to a bituminous binder either with or without the addition of an organo-modified layered silicate. The apparent molecular weight distributions and relaxation spectra were also calculated from the master curves and used to characterize the effect of aging on the binder properties and structure. In this way, an interesting parallelism was observed between the SARA fractions and the populations derived from a deconvolution analysis of the apparent molecular weight distributions.

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.

Environmentally Benign Adhesive Synthesized by Dispersion Copolymerization of Styrene and Butyl Acrylate

2006 ◽  
Vol 11-12 ◽  
pp. 757-760
Author(s):  
Jun Ying Zhang ◽  
Peng Dou
Keyword(s):  
Molecular Weight ◽  
Butyl Acrylate ◽  
Monomer Concentration ◽  
Environmentally Benign ◽  
Functional Monomer ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Stabilizer Concentration ◽  
Ethanol Medium ◽  
Weight Distributions

Environmentally benign adhesive was synthesized by dispersion copolymerization of styrene(St) and butyl acrylate (BA) in an ethanol medium with benzoyl peroxide (BPO) as the initiator and poly(vinylpyrrolidone) as the stabilizer in the presence of acrylic acid(AA) as the functional monomer. The effect of the concentration of stabilizer, initiator and functional monomer on the conversions, molecular weights and molecular weight distributions was investigated. The results show that the conversions almost keep invariable with the increasing of stabilizer concentration, but the molecular weights increase and molecular weight distributions decrease. Conversions increase with the increasing of initiator concentration, but the molecular weights and molecular weight distributions decrease. However with the increasing of functional monomer concentration, conversions and molecular weight distributions increase but the molecular weights decrease.

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