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133 results on '"Picken, S. J."'

9. Optimisation of Proton-Conducting sPEEK Membranes through a Thermal Treatment Method Monitored by Dielectric Spectroscopy

Author

European Commission, Córdova-Chávez, M. E., Hernández, Marianella, Picken, S. J., Kelder, E. M., European Commission, Córdova-Chávez, M. E., Hernández, Marianella, Picken, S. J., and Kelder, E. M.

Abstract

The Sulfonated Poly (Ether Ether Ketone) (sPEEK) is used in many of the developments of polymer electrolyte membranes for fuel cells. In this publication, it is proven that the water in the sPEEK membrane creates channels in the sulfonated clusters by interacting with the sulfonic groups, and changing the glass transition temperature (Tg) of the material. It is shown that, for conductivity, apart from water in the membrane, order is needed in the water channels because it has an impact on how fast the protons pass through the membrane. This research focuses on how various thermal treatment, performed under a pre-stated conditioning; allow the free alignment of the inner phases, influencing their order. It is demonstrated how is possible to use of differential calorimetry, dielectric measurements and X-ray to follow these changes, and how to used Broadband Dielectric Spectroscopy to forecast the most optimal and stable thermal treatment for the highest proton conduction in sPEEK. The methodology is also test successfully on a hybrid sPEEK/Boron Phosphate membrane.

Published
2018

10. Amorphous-amorphous transition in glassy polymers subjected to cold rolling studied by means of positron annihilation lifetime spectroscopy.

Author

Cangialosi, D., Wübbenhorst, M., Schut, H., van Veen, A., and Picken, S. J.

Subjects
POSITRON annihilation, SPECTRUM analysis, ELECTRONS, NUCLEAR reactions, POSITRONS, AMORPHOUS substances
Abstract

In this study, polycarbonate (PC) and polystyrene (PS) are subjected to plastic deformation by means of cold rolling and the resulting variation of the free volume and its subsequent time evolution after rolling is investigated by means of positron annihilation lifetime spectroscopy (PALS). The value of the long lifetime component that is attributed to the decay of ortho-positronium (τo-Ps) and its intensity (Io-Ps) are used to characterize, respectively, the size and the concentration of the free-volume holes. In addition to the PALS experiments, the effect of plastic deformation on the dynamic tensile modulus is investigated. The PALS results show that both for well-aged PC and PS an increase of τo-Ps and a decrease of Io-Ps occur upon plastic deformation. During the subsequent aging, τo-Ps tends to return to the value assumed before plastic deformation, while Io-Ps remains constant with time. These results corroborate the idea of an amorphous-amorphous transition, rather than that of a “mechanical rejuvenation” as proposed in the past to explain the ability of plastic deformation to reinitiate physical aging. Finally, a linear relation between the size of the free-volume holes and the dynamic tensile modulus is found, which suggests that the stiffness of amorphous glassy polymers is fully determined by their nanoscopic structure. [ABSTRACT FROM AUTHOR]

Published
2005
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12. A deuterium nuclear magnetic resonance investigation of orientational order and director kinetics in aramid solutions.

Author

Fan, S. M., Luckhurst, G. R., and Picken, S. J.

Subjects
SULFURIC acid, NUCLEAR magnetic resonance spectroscopy, POLYMERS
Abstract

We have studied the molecular orientational order and director kinetics of the nematic phase formed by dissolving poly-p-phenylene-terephthalamide (PPTA) in sulphuric acid using deuterium NMR spectroscopy. Measurements were made on standard polymer samples using deuterated sulphuric acid and with deuterated PPTA in normal H2SO4. The influence of temperature and polymer concentration on the quadrupolar splittings which reflect the orientational order of the solvent and the solute are reported. The biphasic gap, between the nematic and the isotropic phase, for an 8.84%(w/w) solution was found to be about 10 °C. The influence of polymer concentration on the orientational order of the polymer solute is consistent with the predictions of a modified Maier–Saupe theory. By measuring the time dependence of the spectra the kinetics of field-induced director reorientation has been studied. The reorientation process from a multidomain sample to a uniform director alignment can be adequately described using an approach in which the different domains are decoupled. [ABSTRACT FROM AUTHOR]

Published
1994
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14. On the \u2018Tertiary Structure\u2019 of Poly-Carbenes; Self-assembly of sp3-Carbon Based Polymers into Liquid-Crystalline Aggregates

Author

Franssen, N. M. G., Ensing, B., Hegde, M., Dingemans, T., Norder, B., Picken, S. J., Alberda van Ekenstein, G. O. R., van Eck, E., Elemans, J. A. A. W., Vis, M, Reek, J. N. H., de Bruin, B., Franssen, N. M. G., Ensing, Hegde, Dingemans, Norder, Picken, S. J., Alberda van Ekenstein, G. O. R., van Eck, Elemans, J. A. A. W., Vis, M, Reek, J. N. H., and de Bruin

Published
2013

32. Liquid-crystalline phthalocyanines revisited

Author

Nolte, Roeland J. M., primary, van der Pol, J. F., additional, Neeleman, E., additional, Zwikker, J. W., additional, Nolte, R. J. M., additional, Drenth, W., additional, Aerts, J., additional, Visser, R., additional, and Picken, S. J., additional

Published
2006
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43. Structure and Mechanical Properties of Nanocomposites with Rod- and Plate-Shaped Nanoparticles.

Author

Tuller, Harry L., Knauth, Philippe, Schoonman, Joop, Picken, S. J., Vlasveld, D. P. N., Bersee, H. E. N., Özdilek, C., and Mendes, E.

Abstract

Particle-reinforced polymer composites or compounds have been used for decades to increase the stiffness and strength of polymers and to reduce thermal expansion. Polymer nanocomposites based on exfoliated layered silicates have been developed more recently [11, 23, 24] for improved mechanical properties, barrier properties, and reduced flammability. Polymer nanocomposites are polymers filled with finely dispersed particles that have at least one dimension in the nanometer range. Compared to composites containing larger dispersed particles, nanocomposites have the advantage of achieving the optimal properties at relatively low filler content, resulting in a lower density and better surface smoothness and transparency. This is due to the large aspect ratio and high stiffness of the particles, resulting from the exfoliation of the layered silicate particles. This can be especially favorable for moisture-sensitive polymers like polyamides, which loose a lot of their stiffness under moist conditions [10, 12]. [ABSTRACT FROM AUTHOR]

Published
2007
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