Oxygen solubility and specific volume of rigid amorphous fraction in semicrystalline poly(ethylene terephthalate)

Lin, Jun; Shenogin, Sergei; Nazarenko, S.

doi:10.1016/s0032-3861(02)00278-1

Cited by 174 publications

(180 citation statements)

References 27 publications

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“…However, as shown in Figure 12.5c, when computing the fractional free volume, I 3 v h , the variations in I 3 and τ 3 (hence v h ) compensate, so that I 3 v h shows no statistically significant differences when comparing cold-and melt-crystallized specimens. We note certain analogies between these PALS results and the previously published data on the O 2 permeability of the same samples [Lin et al, 2002], which indicated that in the melt-crystallized specimens, O 2 solubility, S, was higher, but the O 2 diffusion coefficients, D, were smaller than those of the cold-crystallized specimens. These differences compensated so that the permeability, P = SD, showed no significant differences between the two types of materials.…”

Section: Raf (1237)supporting

confidence: 84%

“…The results [Lin et al, 2002] indicate that while the volume fraction of RAF in melt-crystallized PET is smaller than in cold-crystallized PET, the specific volume and hence the fractional free volume are much higher, because of the higher effective vitrification temperature. This enhanced free volume is the source of the higher oxygen solubility of melt-crystallized PET versus cold-crystallized PET.…”

Section: Raf (1237)mentioning

confidence: 87%

“…The resulting mass fractions of the three phases, w MAF , w RAF , and X c , are plotted in Figure 12.4 as a function of the 1-octene content [Kilburn et al, 2002]. Olson et al [2003] carried out PALS studies of 22 poly(ethylene terephthalate) (PET) specimens with varying degrees of crystallinity; 11 specimens were meltcrystallized at 210 • C; and 11 were made via cold crystallization at 110 • C. Each sample was characterized thoroughly by DSC and WAXD in terms of T g , T m , and X c , and, in fact, prior to the PALS investigation, were employed in a study of oxygen permeability at room temperature, which demonstrated that the O 2 solubility in the melt-crystallized PET is higher than in the cold-crystallized PET [Lin et al, 2002]. This earlier work further established that the observed decreases in solubility and diffusion coefficient of oxygen in semicrystalline PET could be explained by the three-phase model of semicrystalline polymers, in which the RAF is considered in addition to the crystalline phase and the MAF.…”

Section: Raf (1237)mentioning

confidence: 99%

“…To test this, the values of I 3RAF v h RAF were estimated, obtained after cooling from the respective crystallization temperature to room temperature by the graphical constructs shown in Figure 12.6. It was assumed, following Lin et al [2002], that the coefficient of thermal expansion of fractional free volume of RAF is the same as that of the normal glass. The values of I 3RAF v h RAF were found to be 24.63 and 15.30 for the meltand cold-crystallized RAF, respectively.…”

Section: Raf (1237)mentioning

confidence: 99%

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Positron Annihilation Lifetime Studies of Free Volume in Heterogeneous Polymer Systems

2010

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474 POSITRON ANNIHILATION LIFETIME STUDIES INTRODUCTIONThe theoretical and experimental background related to the positron annihilation lifetime spectroscopy (PALS) technique and its application as a quantitative probe for free volume in polymeric materials have been discussed extensively in Chapters 10 and 11, so we limit ourselves to a brief overview of these issues by way of introduction and commentary. Our principal focus here is to review what evidence has been generated using the PALS technique to provide insight into three topics of current interest, each of which involves probing specific heterogeneities in the amorphous polymeric phase. The first relates to the existence of concentration fluctuations in miscible polymer blends and their effect on materials properties, such as broadening of the glass transition region. The second concerns the fact that to interpret accurately the properties of certain semicrystalline polymers, such as gas transport, it is necessary to invoke a rigid amorphous phase, believed to involve the disordered chain segments that link crystalline lamellae, whose behavior differs from the usual (mobile) amorphous phase that exists far from the crystalline surface. The third topic involves evidence that a similarly rigid amorphous phase exists in polymeric nanocomposites, associated with polymer chains that lie near the surface of the inorganic particles. PALS AS A PROBE FOR FREE VOLUME IN POLYMERSA PALS experiment involves bringing a polymer sample into contact with a source of positrons, typically 22 Na. Energetic positrons emitted into the polymer by the source are slowed through collisions with atoms, creating an ionized radiation track (positron spur). In the last portion of the spur, referred to as the blob, the positron thermalizes, and either annihilates or finds a secondary electron created by the ionization to form a localized positronium atom Byakov, 2003, 2007;Stepanov et al., 2005a Stepanov et al., ,b, 2007. The spin 1 atom, called ortho-positronium (o-Ps), is three times more likely to form than is the spin 0 atom [para-positronium (p-Ps)] and is more stable than the latter, which annihilates within 125 ps. o-Ps has a long lifetime (140 ns in vacuum), which lifetime is determined by interactions with the medium. Typically, o-Ps annihilates via a pickoff mechanism, with the positron "picked off" by an electron of the medium that has opposite spin. Since o-Ps is easily polarizable, and therefore strongly repelled by the medium, it tends to localize in regions of low electron density (holes or free volume). The lifetime of o-Ps is then determined by the electron density and physical size of the hole in which it finds itself, and normally falls in the range of a few nanoseconds.Typically, therefore, a PALS spectrum consists of a minimum of three components: the short-lived p-Ps component with intensity I 1 and lifetime τ 1 = 125 ps; a free positron annihilation component, with intensity I 2 and lifetime τ 2 ; and the o-Ps component, with intensity I 3 and lifetime τ 3 . ...

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Section: Raf (1237)supporting

confidence: 84%

Section: Raf (1237)mentioning

confidence: 87%

Section: Raf (1237)mentioning

confidence: 99%

Section: Raf (1237)mentioning

confidence: 99%

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Positron Annihilation Lifetime Studies of Free Volume in Heterogeneous Polymer Systems

2010

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“…The existence of rigid amorphous phase in semi-crystalline polymer such as PET is now well recognized and is associated with the region where several lamellas are separated by very thin (2-4 nm) amorphous layers. Even if these regions possess additional free volume upon cooling, which may explain the observed higher solubility [11],it is hard to believe that they can participate to bubble nucleation and growth since they are constrained between crystallites. It is also of interest to point out the work done by Mizoguchi et al [12] on the formation of micro-cavities in semicrystalline systems during the desorption of the CO 2 gas molecules.…”

Section: Introductionmentioning

confidence: 99%

Batch foaming of poly(ε-caprolactone) using carbon dioxide: Impact of crystallization on cell nucleation as probed by ultrasonic measurements

Reignier

Tatibouët

Gendron

2006

Polymer

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The effect of crystallization on the foaming of poly(3-caprolactone), a semi-crystalline biodegradable polymer, was studied using batch processing and CO 2 as the physical blowing agent (PBA). Previous work on the same system suggested that the formation of high cell population densities of small open cells was crystalline fraction dependent. In this work, ultrasonic sensors were used to investigate the effect of crystallization on the cell nucleation mechanism through the monitoring of ultrasonic velocity, attenuation and specific volume characteristics. Analysis of the ultrasonic data allowed to determine the crystallization temperature and thus determined the effect of crystallization on the pressure at which phase separation occurred (degassing pressure). Clearly, the presence of crystals leads to a 5-10-fold increase in the degassing pressure with respect to the amorphous system. In addition, it was shown that the talc content did not significantly influence the degassing pressure for a full amorphous system. However, talc particles can drastically affect the degassing conditions through their role of precursors for crystal formation. Different mechanisms are proposed as possible explanations for the enhancement of cell nucleation in such semi-crystalline polymer systems. Crown

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3D Printed Liquid Crystal Polymer Thermosiphon for Heat Transfer under Vacuum

Seshadri

Hischier

Masania

et al. 2023

Adv Materials Technologies

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A novel approach is presented to 3D print vacuum–tight polymer components using liquid crystal polymers (LCPs). Vacuum–tight components are essential for gas storage and passive heat transfer, but traditional polymer 3D printing methods often suffer from poor interfaces between layers and high free volume, compromising vacuum integrity. By harnessing the unique properties of LCPs, including low free volume and low melt viscosity, highly ordered domains are achieved through nematic alignment of polymer chains. Critical gas–barrier properties are demonstrated, even in thin, single–print line–walled samples ranging from 0.8 to 1.6 mm. A 200 mm evacuated thermosiphon is successfully printed, which exhibits a thermal resistance of up to 2.18 K/W and an effective thermal conductivity of up to 28 W/mK at 60 °C. These values represent a significant increase compared to the base LCP material. Furthermore, the geometric freedom, enabled by 3D printing through the fabrication of complex–shaped thermosiphons, is showcased. The authors study highlights the potential of LCPs as high–performance materials for 3D printing vacuum–tight components with intricate geometries, opening new avenues for functional design. An application of integrating 3D printed thermosiphons as selective heat transfer components in building envelopes is presented, contributing to greenhouse gas emissions mitigation in the construction sector.

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Oxygen solubility and specific volume of rigid amorphous fraction in semicrystalline poly(ethylene terephthalate)

Cited by 174 publications

References 27 publications

Positron Annihilation Lifetime Studies of Free Volume in Heterogeneous Polymer Systems

Positron Annihilation Lifetime Studies of Free Volume in Heterogeneous Polymer Systems

Batch foaming of poly(ε-caprolactone) using carbon dioxide: Impact of crystallization on cell nucleation as probed by ultrasonic measurements

3D Printed Liquid Crystal Polymer Thermosiphon for Heat Transfer under Vacuum

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