Papers by Keyword: Free Volume

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Authors: Masanori Fujinami, Ryutaro Minei, Chang Gui Liu, Kenta Hara
Abstract: The in situ positron annihilation spectroscopy measurement has been developed and applied to investigate the structural change in free volume on the tensile deformation of linear low-density polyethylene. The pick-off lifetime of ortho-positronium (Ps) decreases by applying the strain and an aging variation cannot be observed. On the contrary the fraction of Ps formation gradually decreases day by day and becomes constant after several days. Further, after release of strain, it returns to the original value. The reason is considered to be that the molecular chains become rigid gradually during deformation and they lose the flexibility.
Authors: Dušan Račko
Abstract: In the Present Contribution the Atomistic Structure of the Polymer Melt at 300 K Is Simulated by Means of Molecular Dynamics. the Agreement with an Experimental Density Is Obtained with a Deviation Lower than 1%. the Free Volume Is Analyzed in 1,000 Structures and 6.5 X 108 Cubic Å of Molecular Space. a Model for the Free Volume Cavities Is Proposed. in the Model the Size and Number of the Cavities Can Be Scaled by Three Parameters: Probe Radius, Cavity Depth and Cavity Threshold Volume. the Experimental Values of the Nano-Sized Cavity Volumes as Well as Ortho-Positronium Lifetimes Are Obtained, as Compared to Models with Cylindrical and Spherical Geometry. a Typical Value of the Number Density of Free Volume Cavities at 0.001 Å-3 Is Obtained. the Cavities Have Typically Elongated Shape with a Side-to-Length Ratio 1:2.
Authors: Andrey Askadskii, Egor Afans’ev, Tatyana Matseevich, Marina Popova, Valerii Kondrashchenko, Shi Cheng Qi
Abstract: A calculation method for prediction of water permeability through polymers is suggested. An appropriate equation for calculating the activation free energy of permeability is proposed. The method is based on a set of atomic constants associated with the polymer-water interaction energy. The chemical structure of polymers as well as the degree of crystallininty, temperature, and free volume are taken into account. The method is also applicable for polymeric nanocomposites.
Authors: Fiorenza Quasso, Giovanni Consolati, M. Pegoraro, F. Severini
Authors: Bo Wang, M. Zhang, W.H. Liu, Shao Jie Wang
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