Study of diffusion of water in polyamide-6 using nuclear magnetic resonance intrascopy

Artemov, Dmitri; Samoǐlenko, A. A.; Iordanskii, A. L.

doi:10.1016/0032-3950(89)90301-8

Cited by 3 publications

(2 citation statements)

References 2 publications

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“…In all these NMR imaging studies no attention was paid to the exact amount of water during the uptake process. The signal intensities are directly interpreted as water quantities. , Only D. Y. Artemov pointed out the complexity of the NMR signal of water in nylon. The signal contribution of plasticized polymer, which appears simultaneously with ingressing water, should not be underestimated.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Water Uptake Study in Thin Nylon-6 Films with NMR Imaging

Reuvers

Huinink

Fischer³

et al. 2012

Macromolecules

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Nylon-6 is widely used as an engineering plastic. Compared to other synthetic polymers, nylon-6 absorps significant amounts of water. Although the typical sorbed amounts and diffusivity of water are well-known, less is known about the relation between the diffusivity and the water content. Attempts have been made in the past to obtain such relationship from moisture content profiles as measured with NMR imaging. However, these studies were mainly performed at high temperatures and without a proper calibration of the signal. In particular, at room temperature, far below the T g of dry nylon, plasticizing effects of water will result in a strong contribution of the polymer signal. Therefore, we have studied water uptake in 200 μm nylon-6 films in this temperature range near room temperature with NMR imaging. By calibrating the NMR signal with vapor sorption data, we were able to obtain moisture content profiles. A strongly nonlinear relation between the NMR signal and the moisture was observed at room temperature, which proves that contribution of the polymer to the NMR signal can neither be neglected nor assumed to be constant in time. Furthermore, glass transition temperature measurements combined with the water distribution provide plasticization profiles during water uptake. On the basis of the moisture content profiles, the moisture content dependency of the diffusion coefficient for water uptake is deduced through a Matano−Boltzmann analysis. This relation appeared to be highly nonlinear at room temperature. The self-diffusion coefficient was calculated through combination of the sorption-isotherm and the diffusion coefficient. Exposure of a nylon film to heavy water showed that water affects only a small fraction of the amorphous nylon phase. Water transport most likely occurs in this fraction of the amorphous phase. It is concluded that the heterogeneity of the amorphous phase is an important issue for a profound understanding of water transport in nylon-6 films. ■ INTRODUCTIONPolyamides, also known as nylons, are widely used as engineering plastic and textile fiber mainly due to their excellent properties. In particular, the mechanical properties are attractive for many applications and remain unaffected in a wide range of temperatures. Nylon is also easy to process, for example by extrusion molding, which is reflected in the large variety of geometries encountered in every day life.The chemical structure of nylons consists of amide groups separated by a number of methylene units. Therefore, a variety of polyamides exist, consisting of either one single α,ω aminoacid monomer like nylon-6 (PA6) and nylon-12 or two monomers, a dicarboxylic acid and a diamine like nylon 4.6 or 6.6. The number of successive carbon atoms in the polymer backbone between the amide groups is given by the index and influences material properties such a stiffness, melting point or water absorption.1 The latter feature is especially caused by the hydrophilic character of the amide functionality.Nylons absorb amounts of wat...

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Section: Introductionmentioning

confidence: 99%

Quantitative Water Uptake Study in Thin Nylon-6 Films with NMR Imaging

Reuvers

Huinink

Fischer³

et al. 2012

Macromolecules

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“…26,27 Examining the polymer chemistry (reaction mechanism, chemistry of polymer and effects of treatment processes) and dynamics of water in other types of polyamide materials with different chemistry (i.e., nylons) is routinely examined with NMR. [28][29][30][31] Herein, we examine the use of solid state NMR to extract the diffusion and activation energy barrier for water and salt in polyamide. We have prepared ion-exchanged polyamide membranes where we introduced the polyamide different salt mixtures (ionic strength = 1 and 2M) and different levels of relative humidity (0, 60 and 98%).…”

Section: Introductionmentioning

confidence: 99%

Unravelling Water and Salt transport in Polyamide with Nuclear Magnetic Resonance Spectroscopy

Abbaszadeh

Choi

Chen

et al. 2022

Preprint

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Unraveling water and salt transport in polyamide is of growing importance as the use of reverse osmosis membranes grows in many industries. Here, using solid-state nuclear magnetic resonance (NMR) spectroscopy, we measure the translational diffusion coefficients using pulsed-field gradient NMR, examine ion dynamics with NMR relaxometry, and determine activation energy barriers of hydrogen and sodium ions in ion-exchanged polyamide using variable-temperature NMR. We identify two predominant diffusion components within the spectra associated with bound and unbound hydrogen and sodium ions. We show that the diffusion coefficient of the bound hydrogen ions decreases by 46% while the free hydrogen diffusion coefficient remained constant as the salinity of the mixture increases from 1 M to 2 M. Conversely, the diffusion coefficient of bounded sodium did not change while the unbounded sodium diffusion coefficient decreased by 38% as the salinity of the mixture increases from 1 M to 2 M. Through examining the spin-lattice relaxation time (T1) at various temperatures we reveal that the sodium and hydrogen ion motion decreases with an increase in salinity, and we also report the associated activation energy. We believe these molecular-scale measurements can aid in extending the solution-diffusion model of reverse osmosis membranes.

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