Premium
Water sorption in amorphous poly(ethylene terephthalate)
Author(s) -
Launay A.,
Thominette F.,
Verdu J.
Publication year - 1999
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19990815)73:7<1131::aid-app4>3.0.co;2-u
Subject(s) - sorption , crystallization , amorphous solid , glass transition , dissolution , enthalpy , solubility , diffusion , activation energy , materials science , fick's laws of diffusion , thermodynamics , polymer chemistry , ethylene , polymer , analytical chemistry (journal) , chemistry , crystallography , organic chemistry , adsorption , composite material , physics , catalysis
Abstract The water sorption characteristics of poly(ethylene terephthalate) (PET) amorphous samples of 250 μm thickness have been studied at various temperatures in a saturated atmosphere. Concerning diffusivity, one can distinguish the following two domains characterized by distinct values of the activation energy: E D ≈ 36 kJ mol −1 at T > 100°C, and E D ≈ 42 kJ mol −1 at T < 60°C, with a relatively wide (60–100°C) intermediary domain linked to the glass transition of the polymer. The crystallization of this latter occurs in the time scale of diffusion above 80°C but doesn't change the Fickian character of sorption curves. The equilibrium concentration m ∞ is an increasing function of temperature, but the solubility coefficient S decreases sharply with this latter, with the apparent enthalpy of dissolution Δ H s being of the order of −28 kJ mol −1 at T < 80°C and −45 kJ mol −1 at T > 80°C. Density measurements in the wet and dry states suggest that water is almost entirely dissolved in the amorphous matrix at T < 80°C but forms partially a separated phase at T > 80°C. Microvoiding can be attributed to crystallization‐induced demixing. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1131–1137, 1999