scholarly journals Relationship between the Microstructure and Performance of Graphene/Polyethylene Composites Investigated by Positron Annihilation Lifetime Spectroscopy

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2990
Author(s):  
Xiaobing Han ◽  
Tao Chen ◽  
Yuan Zhao ◽  
Jie Gao ◽  
Yanan Sang ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Volume Fraction ◽  
Quantitative Description ◽  
Interfacial Interaction ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Structure Property ◽  
Positron Annihilation Lifetime ◽  
Free Volume Fraction ◽  
Interaction Intensity

The quantitative characterization of microstructure is most desirable for the establishment of structure-property relationships in polymer nanocomposites. In this work, the effects of graphene on the microstructure, mechanical, electrical, and thermal properties of the obtained graphene/polyethylene (PE) composites were investigated. In order to reveal the structure-performance relationship of graphene/PE composites, especially for the effects of the relative free volume fraction (fr) and interfacial interaction intensity (β), positron annihilation lifetime spectroscopy (PALS) was employed for its quantitative description. The relative free volume fraction fr gives a good explanation of the variation for surface resistivity, melting temperature, and thermal stability, and the variation of tensile strength and thermal conductivity agree well with the results of interfacial interaction intensity β. The results showed that fr and β have a significant effect on the properties of the obtained graphene/PE composites, and the effect on the properties was revealed.

scholarly journals Effect of Free Volume on Curcumin Release from Various Polymer-Based Composite Films Analyzed Using Positron Annihilation Lifetime Spectroscopy

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5679
Author(s):  
Jong-Whan Rhim ◽  
Saygin Kuzeci ◽  
Swarup Roy ◽  
Necmettin Akti ◽  
Cumali Tav ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Bioactive Compounds ◽  
Polymer Matrix ◽  
Volume Fraction ◽  
Composite Films ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime ◽  
Biocomposite Films ◽  
Free Volume Fraction

This work reports the effects of free volume on curcumin release in various polymer-based composite films. Curcumin-reinforced biocomposite films were fabricated with natural biopolymers (carrageenan and chitosan) and bioplastics (poly(lactide) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT)) via the solvent casting method. The curcumin release test was performed using an aqueous medium, and it was found that it was released the fastest in the carrageenan film, followed by the chitosan, PLA, and PBAT films, presumably owing to the dissimilarity of the polymer matrix. The free volume of the polymer films was determined using positron annihilation lifetime spectroscopy (PALS) to understand the release phenomena of curcumin. The free volume fraction was varied and reliant on the type of polymer, with the highest in the PBAT-based film followed by the PLA-, chitosan-, and carrageenan-based films. The free volume method helps analyze the release of bioactive compounds in a polymer matrix and may help to achieve a better understanding of the release of bioactive compounds.

BEYOND THE SPHERICAL APPROXIMATION: ELONGATED FREE VOLUME HOLES IN RUBBERS: A POSITRON ANNIHILATION STUDY

2019 ◽  
Vol 92 (4) ◽  
pp. 709-721
Author(s):  
Giovanni Consolati ◽  
Dario Nichetti ◽  
Francesco Briatico Vangosa ◽  
Fiorenza Quasso
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Volume Fraction ◽  
Spherical Approximation ◽  
Linear Polymers ◽  
Positron Annihilation Lifetime ◽  
Free Volume Fraction ◽  
Conformational Statistics ◽  
Hole Model ◽  
Positron Annihilation Study

ABSTRACT The free volume fraction, a key parameter for the understanding of mechanical and transport properties of polymers, has been evaluated in a fluoroelastomer and a cis-polyisoprene rubber by means of positron annihilation lifetime spectroscopy and dilatometry. The evaluation showed that the assumption of elongated holes allows one to get a very good agreement between the free volume fraction experimentally determined and the theoretical expectation based on the lattice-hole model. On the other hand, systematic discrepancies are found using the spherical approximation. Moreover, the average hole size is found to be correlated to the effective bond length leff, a parameter connected to reptation motions and largely independent of the polymer structure. The result sheds some light on conformational statistics for the most flexible linear polymers that approach Gaussian chain behavior.

scholarly journals Positron Annihilation Lifetime Study on free Volume Changes in TLD by Gamma - irradiation

2004 ◽  
Vol 1 (1) ◽  
pp. 144-148
Author(s):  
Baghdad Science Journal
Keyword(s):  
Gamma Irradiation ◽  
Positron Annihilation ◽  
Free Volume ◽  
Volume Fraction ◽  
Gamma Dose ◽  
Volume Changes ◽  
Positron Annihilation Lifetime ◽  
Free Volume Fraction ◽  
First Time ◽  
Free Volume Hole

Positron annihilation lifetime has been utilized for the first time to investigate the free - volume hole properties in thermolumenscent dosimeter ( TLD ) as a function of gamma-dosc . The hole volume, free volume fraction determined form orthopsitronium lifetime are found to be ?lamatically increase to large values , and then to minimum values as a function ofgamma-dose . The free - volume holes size is found to be 0.163nm’ and to have maximum of 0.166nm^ at the gamma-dose of 0.1 and 0.8 Gy, respectively-

scholarly journals Shape and Temperature Expansion of Free Volume Holes in Some Cured Polybutadiene-Polyisoprene Rubber Blends

2021 ◽  
Vol 22 (3) ◽  
pp. 1436
Author(s):  
Giovanni Consolati ◽  
Eros Mossini ◽  
Dario Nichetti ◽  
Fiorenza Quasso ◽  
Giuseppe Maria Viola ◽  
...  
Keyword(s):  
Free Volume ◽  
Radial Direction ◽  
Volume Fraction ◽  
Spherical Shape ◽  
Suitable Model ◽  
Positron Annihilation Lifetime ◽  
Rubber Blends ◽  
Free Volume Fraction ◽  
Hole Model ◽  
Best Fit

The free volume fraction of a macromolecular structure can be assessed theoretically by using a suitable model; however, it can also be evaluated from experimental data obtained from dilatometry and positron annihilation lifetime spectra. In this second case, a regular geometry of the sub-nanometric cavities forming the free volume has to be assumed, although in fact they are irregularly shaped. The most popular approach is to guess spherical holes, which implies an isotropic growth of these last with temperature. In this work, we compared the free volume fraction, as obtained from experiments in a set of polybutadiene and polyisoprene cured rubbers and their blends, with the analogous quantity expected by using the lattice-hole model. The results allowed us to obtain insights on the approximate shape of the holes. Indeed, a cylindrical flattened geometry of the cavities produced a better agreement with the theory than the spherical shape. Furthermore, the best fit was obtained for holes that expanded preferentially in the radial direction, with a consequent decrease of the aspect ratio with temperature.

Preliminary Positron Lifetime Results on Free Volumes in Cyclodextrins

2010 ◽  
Vol 666 ◽  
pp. 99-102 ◽  
Author(s):  
Maria Fatima Ferreira Marques ◽  
A.M.G. Moreira Da Silva ◽  
P.M. Gordo ◽  
Z. Kajcsos
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Source ◽  
Lifetime Component ◽  
Positron Annihilation Lifetime ◽  
Long Lifetime

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.

Ceramide increases free volume voids in DPPC membranes

RSC Advances ◽  
2015 ◽  
Vol 5 (55) ◽  
pp. 44282-44290 ◽  
Author(s):  
E. Axpe ◽  
A. B. García-Arribas ◽  
J. I. Mujika ◽  
D. Mérida ◽  
A. Alonso ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Lipid Membranes ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime

We have measured by positron annihilation lifetime spectroscopy (PALS) that ceramide increases the size of the free volume holes in DPPC lipid membranes.

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