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Positron studies of the temperature-dependence of free volumes in Polydimethyls...
Marques, M. F. Ferreira; Gordo, P. M.; Kajcsos, Zs.; Gil, C. Lopes; Lima, A. P. de; Queiroz, D. P.; Pinho, M .N. deFree-volume parameters in polyurethane/urea membranes have been studied by positron annihilation lifetime and Doppler broadening measurements. The bi-soft segment membranes were obtained by varying the ratio of the structural constituents, polypropylene oxide and polydimethylsiloxane (PU/PDMS), with PDMS content from 25 to 75 wt%. The free-volume holes determined by PALS are correlated with gas permeation featu...
Free-volume studies in polyurethane membranes by positron annihilation spectros...
Marques, M. F. Ferreira; Gil, C. Lopes; Gordo, P. M.; Kajcsos, Zs.; Lima, A. P. de; Queiroz, D. P.; Pinho, M. N. deThe free-volume parameters in various urethane/urea membranes obtained by varying the ratio of the structural constituents, polypropylene oxide and polybutadiene, were studied by positron lifetime and Doppler broadening measurements. On bi-soft segment membranes, a correlation was found between the composition of membranes, the normalized free volume, the radii of the holes and gas permeability. However, the co...
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