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Title: Free-volume studies in polyurethane membranes by positron annihilation spectroscopy
Authors: Marques, M. F. Ferreira 
Gil, C. Lopes 
Gordo, P. M. 
Kajcsos, Zs. 
Lima, A. P. de 
Queiroz, D. P. 
Pinho, M. N. de 
Keywords: Positronium; Urethane/urea polymers; Phase separation; Permeability; Pore size; Free volume
Issue Date: 2003
Citation: Radiation Physics and Chemistry. 68:3-4 (2003) 573-576
Abstract: The 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 correlation is not clear when PU data are also considered, indicating that other features must also play an important role in the permeation mechanism.
Rights: openAccess
Appears in Collections:FCTUC Física - Artigos em Revistas Internacionais

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