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Influence of backbone rigidity on the curing and the dielectric relaxations of unsaturated polyesters
Author(s) -
Simitzis J.,
Triantou D.,
Soulis S.,
Tsangaris G.,
Zoumpoulakis L.,
Manolopoulos E.
Publication year - 2010
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/app.33295
Subject(s) - phthalic anhydride , adipic acid , materials science , polymer chemistry , styrene , differential scanning calorimetry , glass transition , polyester , curing (chemistry) , fourier transform infrared spectroscopy , dielectric , gloss (optics) , maleic anhydride , organic chemistry , chemistry , composite material , copolymer , chemical engineering , polymer , thermodynamics , coating , physics , optoelectronics , engineering , catalysis
Unsaturated polyesters with maleic acid and different molar ratio of phthalic anhydride to adipic acid were produced, mixed with styrene, and cured. The degree of double bonds conversion, determined by differential scanning calorimetry (α DSC ), indicating the initial curing, increases significantly with the molar ratio of phthalic anhydride. On the other hand, the degree of double bonds conversion of maleate (α UP,FTIR ) and styrene (α St,FTIR ) units determined by Fourier transform infrared spectroscopy after prolonged curing are considerably higher than α DSC and increase slightly with the molar ratio of phthalic anhydride. Polyester containing phthalic anhydride without adipic acid (M5P5) has the lowest tetrahydrofuran uptake and diffusion parameter D /α 2 due to its more rigid segments, in opposite to polyester containing adipic acid (M5A5) having the highest values. According to dielectric spectroscopy measurements, two different relaxations were determined, one beginning above 130°C (with peak above 180°C) attributed to α‐relaxation (dielectric glass transition) and a second one at lower temperatures, attributed to β‐relaxation. The peak of β‐relaxation is at around 130, 75–80, and 30°C for the rigid, intermediate rigidity/flexibility, and flexible polyesters, respectively. The α‐relaxation is determined at low frequencies and the β‐relaxation at intermediate or high frequencies. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011