scholarly journals Apparent Molecular Weight Distributions for Investigating Aging in Polymer-Modified Bitumen

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Miriam Cappello ◽  
Sara Filippi ◽  
Yvong Hung ◽  
Massimo Losa ◽  
Giovanni Polacco
Keyword(s):  
Molecular Weight ◽  
Complex Modulus ◽  
Apparent Molecular Weight ◽  
Strong Impact ◽  
Master Curves ◽  
Modified Bitumen ◽  
Oxidative Aging ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Polymer Modified Bitumen

The oxidative aging of bituminous binders affects the performance and durability of pavements. In the case of polymer-modified binders, aging involves both bitumen and polymers and has a strong impact on the whole architecture of the material. Rheology may help in understanding these structural changes, and interesting information may be obtained by analysing the evolution of apparent molecular weight distributions. This was demonstrated with a bituminous binder modified with a poly(styrene-butadiene) block copolymer and subjected to prolonged artificial aging. Isothermal frequency sweep tests were used to construct master curves of the phase angle and magnitude of the complex modulus. The master curves were then used to calculate relaxation spectra and apparent molecular weight distributions of the binders, as well as simulated temperature sweep tests. A comparison of the behaviour of the base and modified bitumen highlighted the role of the polymer in aging. Polymer degradation significantly damages the elastomeric network, yet the residual polymer chains still interact with the bitumen molecules and reduce their oxidative aging. The apparent molecular weight distributions were deconvoluted to create an aging index specifically developed for polymer-modified bitumen.

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.

Removal of Dissolved Hydrophobic and Hydrophilic Organic Substances during Coagulation/Flocculation of Surface Waters

1993 ◽  
Vol 27 (11) ◽  
pp. 143-152 ◽  
Author(s):  
J. P. Croué ◽  
E. Lefebvre ◽  
B. Martin ◽  
B. Legube
Keyword(s):  
Molecular Weight ◽  
Surface Waters ◽  
Apparent Molecular Weight ◽  
Weight Fraction ◽  
Low Molecular Weight ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Hydrophobic Substances ◽  
Moderate Change ◽  
Final Effluent

Dissolved organic carbon (DOC) from raw and coagulated surface waters was fractionated at acidic pH using two superposed XAD 8 and XAD 4 resin columns, into three fractions : hydrophobic substances (i.e. humic substances) adsorbed on XAD 8, hydrophilic acids adsorbed on XAD 4 and “non-acid” hydrophilics which represent the organics contained in the final effluent. DOC of untreated waters was evenly split between the hydrophobic and hydrophilic fractions. The “non-acid” hydrophilics were generally as or slightly more abundant than the corresponding hydrophilic acids. For three of the six waters studied, DOC distribution was not modified after coagulation/clarification treatment. These waters also exhibited a low reduction in THMFP and TOXFP per unit of DOC after treatment. One water showed moderate change and two a significant change in DOC distribution. With the latter, a large decrease of their THMFP/DOC and/or TOXFP/DOC ratios was observed. As expected, the apparent molecular weight distributions(1000 daltons nominal membrane cutoff) have been shifted toward the low molecular weight fraction. Aluminum coagulation experiments were carried out on isolated humic, fulvic and hydrophilic acids. Humic acids were identified as the most reactive fraction, with a dramatical reduction of their THMFP/DOC and TOXFP/DOC ratios after coagulation. Fulvic and hydrophilic acids were found to react to the same extent with the coagulant, and showed comparable THMFP and TOXFP perunit of DOC before and/or after coagulation.

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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