scholarly journals Ultraviolet Aging Mechanism of Asphalt Molecular Based on Microscopic Simulation

2021 ◽  
Author(s):  
Min min Xiao ◽  
Lín Fan
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Low Temperature ◽  
Molecular System ◽  
Uv Aging ◽  
Distribution Width ◽  
Factors Affecting ◽  
Temperature Resistance ◽  
Ultraviolet Aging

Abstract In order to reveal the nature of the Ultraviolet aging(UV-aging) behavior of asphalt molecules, simulation by Materials Studio software. The effect of UV aging on the transformation, aggregation and motion state of asphalt microstructure is analyzed by the changes in energy, density of dispersive phase, glass transition temperature and viscosity of the asphalt molecular system. The results show that UV aging enhances the bonding degree of asphalt molecules by increasing the heavy components in the asphalt molecules and increasing the distribution width between the asphalt molecule components, which improves the high-temperature resistance of asphalt. At the meantime, the UV aging causes the asphalt molecular movement state to solidify at low temperature so that the rheological behavior is difficult to occur by reducing the lightweight component and free volume of the asphalt molecule and increasing the glass transition temperature, which reduces the low-temperature resistance of asphalt. In addition, among the factors affecting the viscosity of asphalt molecular, the degree of influence of the molecular structure and molecular weight is significantly greater than the molecular activity. The addition of short branched chain hydrocarbon molecules to the UV-aged asphalt molecules could effectively reduce the viscosity of the asphalt molecules and improve the flowability of the asphalt molecules. The results of the study contribute to the understanding of the characteristics of changes in the microstructural pattern and dynamic behavior of asphalt molecules during UV aging, and achieve interpretation and prediction of changes in asphalt properties at the microscopic level.

Citric acid grafting onto polyurethane for the control of molecular interactions and water compatibility

2016 ◽  
Vol 48 (8) ◽  
pp. 691-710
Author(s):  
Yong-Chan Chung ◽  
Hyeryoung Yoon ◽  
Jae Won Choi ◽  
Byoung Chul Chun
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Citric Acid ◽  
Low Temperature ◽  
Molecular Interactions ◽  
Water Permeability ◽  
Enthalpy Change ◽  
Low Temperature Flexibility ◽  
Grafting Onto

Citric acid (CA) was used as a grafted group onto polyurethane (PU) to form a CA-grafted PU series, with a control PU series containing free CA prepared for comparison. With an increase in the CA content, the enthalpy change during the melting increased for the PU and CPU series, and the glass transition temperature increased with the increase in CA content for the PU series but not for the CPU series. The tensile strengths of the PU series sharply increased with the CA content, whereas those of the CPU series did not. The PU series demonstrated better low-temperature flexibility and water permeability than the unmodified PU.

Cryomicroscopy of Latex and Latex Films

2000 ◽  
Vol 6 (S2) ◽  
pp. 316-317
Author(s):  
O. L. Shaffer ◽  
M. S. El-Aasser
Keyword(s):  
Electron Microscopy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Low Temperature ◽  
Protective Coatings ◽  
Continuous Film ◽  
The Core ◽  
Film Forming ◽  
Water Uses

Latexes are dispersions of homopolymers and copolymers, usually in water. Uses of these latexes are many such as protective coatings and adhesives. In order to form a continuous film the polymer must have film forming properties such as a low glass transition temperature (Tg). Latexes are being designed such as one polymer in the core of the particle and a shell of another polymer or perhaps a series of shell layers. Microscopy has become a powerful tool in the examination of the morphology of the latex particles. Because of the use of low Tg polymers, sample preparation and examination by electron microscopy at temperatures above the Tg of the polymer causes the particles to become distorted and no longer representative of their true morphology. Low temperature methods therefore have become crucial in the field of latex microscopy.

Temperature Dependence of Free Volume in Epoxy/Rectorite Nanocomposites by Positron Annihilation

2008 ◽  
Vol 607 ◽  
pp. 210-212
Author(s):  
Ming Zhang ◽  
Shao Jie Wang ◽  
L.M. Liu ◽  
Peng Fei Fang
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Viscous Flow ◽  
Polymer Nanocomposites ◽  
Free Volume ◽  
Softening Temperature ◽  
Flow Temperature

Recently polymer nanocomposites[1,2] have been receiving special attention because of its advantages and unique properties in comparison to the traditional polymer composites.The structural transformation of Epoxy (cured by polyamide) and epoxy/Rectorite nanocomposite(with 0.5% rectorite content) is studied by PALS as a function of temperature from 30K to 490K. For Epoxy and Epoxy/Rectorite nanocomposite, the glass transition temperature (Tg) is observed to be 270K and 260K, the second transition temperature (Tγ) is 160K and 120K, the viscous flow temperature (Tf) is the same as 380K. The result shows that properties of the free-volume in nanocomposite have been changed by the rectorite platelets fully separated in material at low temperature. At the same time, we find that the intensity of o-Ps decreases with increase of the temperature at the softening temperature above the Te.

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