Rate of gas transport in glassy polymers: a free volume based predictive model

Ganesh, K. N.; Nagarajan, Ramaswamy; Duda, J. L.

doi:10.1021/ie00003a016

Cited by 41 publications

(22 citation statements)

References 23 publications

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“…approach suggests that the exothermal solvent uptake characterised by ln ␥ 1 Ͻ 1 at low solvent concentrations proceeds by adsorption into pre-existing sites provided by the excess free volume of polymers at T Ͻ T g . The same phenomenology is reported for gas adsorption by glassy polymers with a sorption following Henry's law above T g , whereas below T g , the gas sorption first follows Langmuir adsorption phenomenology prior to recovery of the Henry mode at higher partial pressures (Paul, 1985;Ganesh et al, 1992).…”

Section: Sorption and Swellingsupporting

confidence: 64%

“…The sigmoidal (plain line) is typical for water sorption by a hydrophilic polymer frozen in a glassy state at low water activity (McLaren and Rowen, 1951;Benczédi et al, 1998). The corresponding gas adsorption phenomenology in polymer glasses is shown in the insert, where c is the ratio of gas to polymer volume at standard temperature, T , plotted as a function of the gas pressure, p (Paul, 1985;Ganesh et al, 1992). approach suggests that the exothermal solvent uptake characterised by ln ␥ 1 Ͻ 1 at low solvent concentrations proceeds by adsorption into pre-existing sites provided by the excess free volume of polymers at T Ͻ T g .…”

Section: Sorption and Swellingmentioning

confidence: 99%

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Useful Principles to Predict the Performance of Polymeric Flavour Delivery Systems

Benczédi

2010

Food Flavour Technology

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In this chapter, we review semi-empirical principles of chemical engineering that are particularly useful to understand the phase behaviour of glassy polymers applied to encapsulate flavours and fragrances. Hildebrand's solubility parameter is used to outline how the polarity of a polymer increases its cohesive energy density, its density, its glass transition temperature and how it reduces its permeability towards apolar molecules such as gaseous oxygen and most flavouring ingredients. Flory's model of polymer solutions is coupled to a generalised Freundlich adsorption model to highlight the limiting phase behaviour of polar polymer glasses at low partial pressures of water and of hydrogels at the saturation vapour pressure of water.This approach suggests that sigmoidal vapour sorption phenomenology is the macroscopic fingerprint of glassy materials. Below the glass transition point, water sorption is therefore assumed to take place on the pre-existing sites formed by an excess free volume, which characterises glassy polymers. This excess free volume needs typically to be minimised in controlled release applications to minimise the diffusion of oxygen and flavour molecules. Mass transport is further described with Fick's laws of diffusion to highlight the effects of polymer cross-linking or plasticisation, as induced by temperature or partial pressure of water. Diffusion-controlled kinetics, scaling with the square root of time, is distinguished from zero-order kinetics observed when mass transport is polymer relaxation-controlled. INTRODUCTIONThe encapsulation of flavours was initially motivated by the need to protect volatile food components from evaporation and oxidation by locking them in a solid carrier able to dissolve rapidly in water (Schultz et al., 1956). Nowadays, more emphasis is laid on slowing aqueous dissolution down and on triggered release systems activated typically by heat and mechanical stress. Controlled flavour release thus provides new solutions to the food industry and enables the development of innovative consumer goods. In this context, the primary objective of flavour delivery systems is to maximise flavour perception by generating impact and persistence when needed.Flavours are traditionally encapsulated by spray-drying an aqueous polymer solution, and the resulting glassy powders have a fine granulometry, favouring quick aqueous dissolution. The selective retention of flavour molecules as water evaporation proceeds during

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Section: Sorption and Swellingsupporting

confidence: 64%

Section: Sorption and Swellingmentioning

confidence: 99%

Useful Principles to Predict the Performance of Polymeric Flavour Delivery Systems

Benczédi

2010

Food Flavour Technology

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“…On the other hand, gas diffusion through polymers in the glassy state is generally viewed as taking place by discrete jumps between two neighboring holes of static free volume (hole free volume) through the formation and relocation of dynamic free volume channels (excess hole free volumes) 62–64. These excess holes cease to exist above the T g and hence do not influence transport properties in the rubbery domain.…”

Section: Resultsmentioning

confidence: 99%

Influence of the nanofiller type and content on permeation characteristics of multifunctional NR nanocomposites and their modeling

Bhattacharya

Biswas

Bandyopadhyay

et al. 2011

Polymers for Advanced Techs

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Along with other properties, superior gas permeation behavior would impart an extra dimension to multifunctional natural rubber (NR) nanocomposites used in various applications, like tires. For the first time, the impact on thermodynamics and kinetics of oxygen transport has been evaluated for nano, micro, and dual filler based multifunctional NR nanocomposites through oxygen permeation studies at three different temperatures. It is seen that, the kinetics is less affected by platelet like nanofillers, while the thermodynamics and eventual permeability are not altered much by fibrous nanofillers. The permeability of the nanocomposites decreased in the presence of nanofillers due to high aspect ratio and exquisite dispersion, as ascertained from morphological studies, which caused increment in tortuosity and the reduction in free volume. Relative permeabilities were compared to predictions of existent permeation models and a novel function was successfully introduced to address deviations in a model. Finally, nearly 60% decrement in permeability of dual filler based nanocomposites explained by the formation of zeta potential driven filler associations indicate potency in development of thinner, but stronger and more durable multifunctional materials with longer air retention capabilities. These could be applied in tire research to reduce material, energy costs and increase fuel efficiencies.

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“…Reduction in oxygen permeation can possibly be achieved by the reduction of available free volume and this reduction in free volume can either be attained by affecting the crystalline morphology of polymer chains or by restricting the chain mobility with the creation of crosslinking sites in the amorphous region of semicrystalline polymeric materials. [32][33][34] These crosslinking networks should be provided by the presence of hydrogen bonding resulting in the improved barrier performance. [35] Furthermore, the availability of moieties can also result in the reduction of polymer free volume by the creation of crosslink (hydrogen bonding) networking.…”

Section: Oxygen Transmission Ratementioning

confidence: 99%

High performance Nylon12/clay nanocomposites for potential packaging applications

Gill

Abid

Song

2020

J of Applied Polymer Sci

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The barrier property enhancement of polymers is presently a matter of great concern for the manufacturing of food packaging and films with excellency in moisture and gas resistance. The objective of this work was to enhance the barrier performance of Nylon12/kaolin clay nanocomposites against water vapors and oxygen. Kaolin clays of different aspect ratios were utilized for nanocomposites manufacturing. Nanocomposites were prepared in twin screw extruder operating at 160–200°C, with an increment of 10°C, and at 110 rev/min. The loading of clay was varied from 1 to 5 wt%. Scanning electron microscopy and X‐ray diffraction characterizations were used to investigate the morphological properties of nanocomposites. The transmission electron microscopy analysis was used to confirm the dispersion of clays in Nylon12 matrix. Enhancement in barrier performance of nanocomposite was noticed at 5 wt% clay loading. Oxygen barrier of nanocomposites was observed to be more prominent than water vapors owing to the presence of hydrogen bonding in Nylon12 structure which restricted oxygen passage. Experimental barrier values of nanocomposites were also fitted on barrier models namely Nielsen, Cussler model, and Gusev‐Lutsi model.

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Rate of gas transport in glassy polymers: a free volume based predictive model

Cited by 41 publications

References 23 publications

Useful Principles to Predict the Performance of Polymeric Flavour Delivery Systems

Useful Principles to Predict the Performance of Polymeric Flavour Delivery Systems

Influence of the nanofiller type and content on permeation characteristics of multifunctional NR nanocomposites and their modeling

High performance Nylon12/clay nanocomposites for potential packaging applications

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