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- Title
Revisiting the thermal relaxations of poly(vinyl alcohol).
- Authors
Betzabe Gonzalez-Campos, J.; Garcia-Carvajal, Zaira Y.; Prokhorov, E.; Luna-Barcenas, J. Gabriel; Mendoza-Duarte, M. E.; Lara-Romero, Javier; del Rio, Rosa E.; Sanchez, Isaac C.
- Abstract
The molecular dynamics of poly(vinyl alcohol) (PVA) were studied by dielectric spectroscopy and dynamic mechanical analysis in the 20-300°C range. The well-established plasticizing effect of water on the glass-transition temperature ( T g) of PVA was revisited. Improper water elimination analysis has led to a misinterpretation of thermal relaxations in PVA such that a depressed T g for wet PVA films (ca. 40°C) has been assigned as a secondary β relaxation in a number of previous studies in the literature. In wet PVA samples, two different Vogel-Fulcher-Tammann behaviors separated by the moisture evaporation region (from 80 to 120°C) are observed in the low- (from 20 to 80°C) and high- (>120°C) temperature ranges. Previously, these two regions were erroneously assigned to two Arrhenius-type relaxations. However, once the moisture was properly eliminated, a single non-Arrhenius α relaxation was clearly observed. X-ray diffraction analysis revealed that the crystalline volume fraction was almost constant up to 80°C. However, the crystallinity increased approximately 11% when temperature increased to 180°C. A secondary β c relaxation was observed at 140°C and was related to a change in the crystalline volume fraction, as previously reported. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
- Subjects
POLYVINYL alcohol; SPECTRUM analysis; DYNAMIC mechanical analysis; X-ray diffraction; MOLECULAR dynamics
- Publication
Journal of Applied Polymer Science, 2012, Vol 125, Issue 5, p4082
- ISSN
0021-8995
- Publication type
Article
- DOI
10.1002/app.33615