Role of free volume characteristics of polymer matrix in bulk physical properties of polymer nanocomposites: A review of positron annihilation lifetime studies

Sharma, S.K.; Pujari, P. K.

doi:10.1016/j.progpolymsci.2017.07.001

Cited by 109 publications

(66 citation statements)

References 177 publications

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“…Studies carried out by positron annihilation spectroscopy (PALS) have estimated the radius of the so-called "holes" (related to the free volume) in glassy polymers to be in the region of 0.26-0.27 nm, while the volume is estimated to be in the region of 5.0-8.0 nm 3 [7,41,48,49]. To place these dimensions in perspective the radius of the "hole" is approximately equal to the radius of the sphere occluding the structure of urea [50] and twice that of a water molecule.…”

Section: The Additivity Rule Free Volume and "Holes"mentioning

confidence: 99%

Antiplasticization of Polymer Materials: Structural Aspects and Effects on Mechanical and Diffusion-Controlled Properties

et al. 2020

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Antiplasticization of glassy polymers, arising from the addition of small amounts of plasticizer, was examined to highlight the developments that have taken place over the last few decades, aiming to fill gaps of knowledge in the large number of disjointed publications. The analysis includes the role of polymer/plasticizer molecular interactions and the conditions leading to the cross-over from antiplasticization to plasticization. This was based on molecular dynamics considerations of thermal transitions and related relaxation spectra, alongside the deviation of free volumes from the additivity rule. Useful insights were gained from an analysis of data on molecular glasses, including the implications of the glass fragility concept. The effects of molecular packing resulting from antiplasticization are also discussed in the context of physical ageing. These include considerations on the effects on mechanical properties and diffusion-controlled behaviour. Some peculiar features of antiplasticization regarding changes in Tg were probed and the effects of water were examined, both as a single component and in combination with other plasticizers to illustrate the role of intermolecular forces. The analysis has also brought to light the shortcomings of existing theories for disregarding the dual cross-over from antiplasticization to plasticization with respect to modulus variation with temperature and for not addressing failure related properties, such as yielding, crazing and fracture toughness.

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Section: The Additivity Rule Free Volume and "Holes"mentioning

confidence: 99%

Antiplasticization of Polymer Materials: Structural Aspects and Effects on Mechanical and Diffusion-Controlled Properties

et al. 2020

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“…Jean et al have estimated the value of C = 0.0018 nm −3 using many polymers. The value of C cannot be used for all the polymers due to variation in their chemistry and hence, the relative fractional free volumes calculated using C = 1 nm −3 [24]. Usually, we use relative fractional free volume where, All these components were determined by the fit's variance ranged from 0.96 to 1.14.…”

Section: Measurementsmentioning

confidence: 99%

“…The free volume available in interphase region mainly depends on the interaction between polymer molecules and the nanofillers. In case of semicrystalline polymers, nanofillers can act as nucleating agents reducing the chain mobility [24]. This leads to a decrease in the free volume in the polymer matrix.…”

Section: Positron Annihilation Lifetime Spectroscopy (Pals)mentioning

confidence: 99%

Effect of Gamma irradiation on the nanofree volume and electrical properties of PVA/PEG/reduced graphene oxide nanocomposites

Abdelmaqsoud

Moh́sen

Hassan

et al. 2019

Arab Journal of Nuclear Sciences and Applications

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Reduced graphene oxide (RGO) doped polyvinyl alcohol/ polyethylene glycol (PVA/PEG) films were prepared by solution casting technique and exposed to 100 gamma radiation. The structural modifications in the samples before and after irradiation were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry DSC. The free volume holes V f determined from the ortho-positronium (o-Ps) lifetime (τ 3) measured by the positron annihilation spectroscopy (PALS) is found to decrease from (84.52 to 67.24Å 3) and from (85.67 to 78.21 Å 3) for nonirradiated and irradiated samples respectively with increasing the nanoscale RGO filler content into the polymer matrix. The resulting decrease of the free volume holes size due to this incorporation could be explained by both the formation of hydrogen-bonding and crosslinking between RGO and PVA/PEG blend as confirmed by XRD and FTIR measurements. This also caused a decrease in the concentration of free volumes F r for both nonirradiated and irradiated samples. The increased D.C. electrical conductivity with increasing RGO volume fraction (0-0.265) suggests a conductivity chain formation through the nanoparticle aggregation. The deduced Ln σ is found to be positively correlated with the probability of free annihilation of positrons I 2 trapped at crystalline-amorphous interfaces. The D.C. conductivity results could be successfully fitted using the model suggested by Miyamoto and Shibayama. The critical free volumes for the charge carriers transport has been deduced to be 80.34 and 82.16Å 3 for nonirradiated and irradiated samples respectively.

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“…Physical properties of polymers and polymer composites depend on the size and size distribution of free volume holes [15]. Positron Annihilation Lifetime Spectroscopy (PALS) was used to follow the changes taking place in the sizes of free volume holes in the PP nanocomposites prepared with different compatibilizers.…”

Section: Determination Of Sizes Of Free Volume Holesmentioning

confidence: 99%

Improvement of Filler-Matrix Interactions in Polypropylene/Montmorillonite Nanocomposites by Usıng Irradiated Polypropylene

Zengin¹,

Çağlayan²,

İde³

et al. 2018

Preprint

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In the preparation of polymer-clay nanocomposites the chemical incompatibility between the clay surface and polyolefins can be overcome by using clays organically modified with short chain organic cations. The compatibility can be further enhanced by using functionalized polymer that wets the clay surface while being miscible with the non-polar polymer matrix. In this work we tried to modify the host polymer polypropylene (PP) by irradiating it with gamma-rays in air knowing that it undergoes oxidation and chain scission simultaneously. Thus lower molecular weight PP with highly polar surface due to oxidation can be expected to play double role of clay modifier and functional compatibilizer. This has been observed to be the case. Finely ground PP granules were irradiated in air in a 60Co γ-irradiator at the dose rate of 0.08 kGy/h (low dose rate to enhance oxidation) to 5, 10, and 20 kGy total doses. The extent of oxidation and change in molecular weight were determined by ATR-FTIR and Melt Flow Rate measurements respectively. PP/MMT nanocomposites were prepared by using 20% γ-PP, 1-5 % MMT and pristine PP to make up the total 100 in a torque rheometer. Maleated PP was also used in similar quantities to compare the effectiveness of γ-PP as a compatibilizing agent. Nanocomposites prepared with 10 kGy irradiated PP was found to show optimum mechanical properties among all formulations, with 26% increase in E-modulus and 10% increase in tensile strength as compared to pristine PP. Ternary PP nanocomposites were characterized by XRD, SAXS and PALS studies.

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Role of free volume characteristics of polymer matrix in bulk physical properties of polymer nanocomposites: A review of positron annihilation lifetime studies

Cited by 109 publications

References 177 publications

Antiplasticization of Polymer Materials: Structural Aspects and Effects on Mechanical and Diffusion-Controlled Properties

Antiplasticization of Polymer Materials: Structural Aspects and Effects on Mechanical and Diffusion-Controlled Properties

Effect of Gamma irradiation on the nanofree volume and electrical properties of PVA/PEG/reduced graphene oxide nanocomposites

Improvement of Filler-Matrix Interactions in Polypropylene/Montmorillonite Nanocomposites by Usıng Irradiated Polypropylene

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