Direct computation of the free volume fraction in amorphous polymers from positron lifetime measurements

2000 ◽  
Vol 61 (13) ◽  
pp. 8784-8792 ◽  
Author(s):  
P. Bandžuch ◽  
J. Krištiak ◽  
O. Šauša ◽  
J. Zrubcová
Keyword(s):  
Free Volume ◽  
Positron Lifetime ◽  
Volume Fraction ◽  
Amorphous Polymers ◽  
Direct Computation ◽  
Lifetime Measurements ◽  
Free Volume Fraction

The Absolute Free Volume Fraction in Polymers from the Positron Lifetime Measurements

2001 ◽  
Vol 363-365 ◽  
pp. 269-271 ◽  
Author(s):  
Jozef Krištiak ◽  
P. Bandžuch ◽  
O. Šauša ◽  
J. Zrubcová ◽  
Josef Bartoš
Keyword(s):  
Free Volume ◽  
Positron Lifetime ◽  
Volume Fraction ◽  
Lifetime Measurements ◽  
Free Volume Fraction ◽  
The Absolute

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.

scholarly journals POSITRON LIFETIME MEASUREMENTS IN NATURAL RUBBER WITH DIFFERENT FILLERS

2013 ◽  
Vol 22 ◽  
pp. 112-117 ◽  
Author(s):  
A. MANDAL ◽  
S. MUKHERJEE ◽  
S. PAN ◽  
A. SENGUPTA
Keyword(s):  
Natural Rubber ◽  
Positron Annihilation ◽  
Free Volume ◽  
Positron Lifetime ◽  
Amorphous Region ◽  
Filler Concentration ◽  
Lifetime Measurements ◽  
Positron Annihilation Lifetime

Positron annihilation lifetime spectra (PLAS) have been measured for natural rubber polymer with different fillers (Titenium dioxide, Nanosilica and Nanoclay) as a function of filler concentration to investigate how these fillers affect the microstructure of free volume of natural rubber. The lifetime spectra is analyzed by using LT9.0 and the longest lived component(τo-Ps) is attributed to the pick- off annihilation of o-Ps in free volume sites, available mostly in the amorphous region of polymer. On the basis of the τo-Ps values the radii of the free volume holes (Rh) are calculated. The PALS results show that o-Ps lifetime as well as the size of free volume decreases with the increase of filler concentration.

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.

The molecular dynamics of different relaxation modes in asymmetric chlorinated butyl rubber/petroleum resin blends

RSC Advances ◽  
2014 ◽  
Vol 4 (40) ◽  
pp. 20620-20625 ◽  
Author(s):  
Fengshun Zhang ◽  
Guansong He ◽  
Kangming Xu ◽  
Hong Wu ◽  
Shaoyun Guo
Keyword(s):  
Molecular Dynamics ◽  
Free Volume ◽  
Volume Fraction ◽  
Butyl Rubber ◽  
Segmental Motion ◽  
Petroleum Resin ◽  
Free Volume Fraction ◽  
Relaxation Modes ◽  
Chlorinated Butyl Rubber

The PR plays a role like an anti-plasticizer in decreasing the free volume fraction of the CIIR/PR blend. The mobility of Rouse modes is confined significantly more than that of local segmental motion.

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.

Study of the free volume fraction in polylactic acid (PLA) by thermal analysis

2015 ◽  
Vol 29 (31) ◽  
pp. 1550226 ◽  
Author(s):  
A. Abdallah ◽  
N. Benrekaa
Keyword(s):  
Free Volume ◽  
Volume Fraction ◽  
Mechanical Analysis ◽  
Poly Lactic Acid ◽  
High Modulus ◽  
Free Volume Fraction ◽  
Elongation Percentage ◽  
Thermal Techniques ◽  
Do So ◽  
Thermoplastic Properties

The poly (lactic acid) or polylactide (PLA) is a biodegradable polymer with high modulus, strength and thermoplastic properties. In this work, the evolution of various properties of PLA is studied, such as glass transition temperature, mechanical modules and elongation percentage with the aim of investigating the free volume fraction. To do so, two thermal techniques have been used: the dynamic mechanical analysis (DMA) and dilatometry. The results obtained by these techniques are combined to go back to the structural properties of the studied material.

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