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Ultrasonic characterization of the kinetics of water sorption in hydrogels
Author(s) -
Maffezzoli A.,
Tarzia A.,
Cannoletta D.,
Montagna G.,
Luprano V. A. M.
Publication year - 1999
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19991380119
Subject(s) - sorption , self healing hydrogels , crystallinity , vinyl alcohol , materials science , polymer , kinetics , glass transition , plasticizer , ultrasonic sensor , chemical engineering , polymer chemistry , composite material , chemistry , acoustics , physics , adsorption , quantum mechanics , engineering
Abstract A complex mechanism characterizes the water uptake kinetics in hydrogels, as a consequence of the strong structural changes occurring in the material during the sorption process. Water acts as a plasticizer, reducing the glass transition temperature of the polymer below the sorption temperature and determining a glass transition in the polymer. In this study the changes in the ultrasonic attenuation and velocity in semicrystalline Poly‐vinyl‐alcohol (PVA) hydrogel films during water sorption are measured by a pulse‐echo system. The ultrasonic wave propagation is applied to monitor the position of the swollen/unswollen fronts and to the measurement of velocity and attenuation. The structural changes in PVA hydrogels, monitored by Wide Angle X‐ray Diffractometry (WAXD), performed during the sorption process, are correlated with the ultrasonic data.