Effect of Temperature on the Free Volume in Glassy Poly(ethylene terephthalate)

Wang, B.; Wang, Z. F.; Zhang, M.; Liu, W. H.; Wang, S. J.

doi:10.1021/ma0120963

Cited by 36 publications

(32 citation statements)

References 20 publications

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“…For most of the polymers, Ps formation in (the densely packed) crystals could not be observed; [71] an extra lifetime of about 1 ns attributed to polymer crystals has only been confirmed for polyethylene and poly(tetrafluoroethylene). [68] The analysis of our spectra from below the melting point using the routines CONTIN, MELT, and LT9.0 did not show any indication of an extra, medium o-Ps lifetime.…”

Section: Positron Lifetime Spectra and Their Analysesmentioning

confidence: 99%

Temperature Dependence of Free Volume in Pure and Silica‐Filled Poly(dimethyl siloxane) from Positron Lifetime and PVT Experiments

Dlubek

Pionteck

et al. 2005

Macro Chemistry & Physics

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Summary:The microstructure of the free volume and its temperature dependence in two poly(dimethyl siloxane)s (PDMS), one in the pure state and the other filled with 35 wt.‐% of an in situ hydrophobized fumed silica with a specific surface area of 200–300 m2 · g−1, were studied by pressure‐volume‐temperature experiments (PVT, T = 22–156 °C, P = 10–200 MPa) and positron annihilation lifetime spectroscopy (PALS, T = −173–100 °C, P = 10−5 MPa). The Simha‐Somcynsky equation of state was used to estimate the hole free volume fraction, h, and free and occupied volumes, Vf = hV and Vocc = (1 − h)V, from the specific total volume, V. The PALS spectra were analyzed with the routine LT9.0, which allowed for a dispersion, σi, in all three of the lifetimes: the para‐positronium (p‐Ps, τ1), positron (e+, τ2), and ortho‐positronium (o‐Ps) lifetime (τ3). This kind of analysis delivered correct p‐Ps lifetime parameters, τ1, σ1, and I1. It was speculated that e+, like o‐Ps, undergoes Anderson localization at empty sites of the, static or dynamic, disordered structure. The hole size distribution, its mean value, 〈vh〉, and dispersion, σh, were calculated from the o‐Ps lifetimes. A comparison of 〈vh〉 with Vf was used to estimate the specific hole number, $N'_{\rm h}$. During melting of the semicrystalline samples at−38 °C (Tm), 〈vh〉 increased abruptly, and σh suddenly decreased. Both effects are explained by the disappearance of the rigid‐amorphous fraction (RAF) and, thus, a reduction in the dynamic heterogeneity. The following leveling‐off in 〈vh〉 and the low value of σh are attributed to the fast segmental relaxation in the PDMS melts which leads to a smearing of the molecule density distribution around a hole during the o‐Ps lifetime. magnified image

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Section: Positron Lifetime Spectra and Their Analysesmentioning

confidence: 99%

Temperature Dependence of Free Volume in Pure and Silica‐Filled Poly(dimethyl siloxane) from Positron Lifetime and PVT Experiments

Dlubek

Pionteck

et al. 2005

Macro Chemistry & Physics

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“…Positron annihilation lifetime spectroscopy has been used as a unique technology to probe the free volume properties of polymers for many years 11, 12. PALS was proven to be sensitive to atom‐scale free volume holes of polymers, due to the formation of the positronium (Ps) atom, which is a bound state of e + and e − .…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the fractional free volume f is evaluated in terms of the o ‐Ps intensity I 3 and the size of free volume hole ( $V={4\over 3}{\rm \pi}R^3$ ): where C is a constant. Usually, we use apparent free volume fraction, f app : because what we concerned is not the absolute value of free volume fraction, but instead the variation of free volume fraction 12…”

Section: Introductionmentioning

confidence: 99%

Investigation of free volume, interfacial, and toughening behavior for cyanate ester/bentonite nanocomposites by positron annihilation

Wang

Feng

et al. 2006

J of Applied Polymer Sci

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Effects of filler on microstructure and toughening behavior of cyanate ester (CE)/bentonite (BT) nanocomposites with different content of BT have been studied by positron annihilation lifetime spectroscopy, X-ray diffraction, transmission electron microscopy, dynamic mechanical analysis, etc. The interesting results found by PALS indicate that the size and concentration of the free volume holes and the apparent free volume fraction increased with increasing the content of BT, which indicates that adding nano-layers to thermosetting materials can lead to the high crosslinking density structure ''looser.'' The experimental results reveal that the increases in size of free volume holes and apparent free volume fraction are related to the increasing conversion of cure reaction. On the other hand, the mechanism of toughening (by adding the nano-clay to the thermosetting material) has been discussed by combining free volume and interfacial property. It is shown that, for the high crosslinking thermosetting material-based nanocomposites, both the property of free volume and dispersion state of nano-layers are the two key factors in determining toughening property.

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“…[4][5][6][7] Utraki et al reported the free-volume fraction of an exfoliated poly(e-caprolactam) (PA-6)/montmorillonite (MMT) nanocomposite estimated by pressure-volumetemperature (PVT) measurement. Compared with the matrix, incorporation of 1.6 wt.-% MMT reduced the freevolume fraction by 14%.…”

Section: Introductionmentioning

confidence: 99%

Free Volume of Montmorillonite/Styrene‐Butadiene Rubber Nanocomposites Estimated by Positron Annihilation Lifetime Spectroscopy

Wang

Zhang

et al. 2004

Macromol. Rapid Commun.

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Summary: The size and concentration of free‐volume holes of two kinds of montmorillonite (MMT)/styrene‐butadiene rubber (SBR) nanocomposites were investigated by positron annihilation lifetime spectroscopy (PALS). Strong interfacial interaction caused an apparent reduction of the free‐volume fraction of rubber probably by depressing the formation of free‐volume holes in the interfacial region. Interfacial interaction in MMT/SBR nanocomposites was weaker than that in SBR filled with carbon black.Dependence of normalized o‐Ps intensity of four kinds of composites on filler volume fraction.imageDependence of normalized o‐Ps intensity of four kinds of composites on filler volume fraction.

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Effect of Temperature on the Free Volume in Glassy Poly(ethylene terephthalate)

Cited by 36 publications

References 20 publications

Temperature Dependence of Free Volume in Pure and Silica‐Filled Poly(dimethyl siloxane) from Positron Lifetime and PVT Experiments

Temperature Dependence of Free Volume in Pure and Silica‐Filled Poly(dimethyl siloxane) from Positron Lifetime and PVT Experiments

Investigation of free volume, interfacial, and toughening behavior for cyanate ester/bentonite nanocomposites by positron annihilation

Free Volume of Montmorillonite/Styrene‐Butadiene Rubber Nanocomposites Estimated by Positron Annihilation Lifetime Spectroscopy

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