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DSC curing study of catalytically synthesized maleic‐acid‐based unsaturated polyesters
Author(s) -
Simitzis J,
Zoumpoulakis L,
Soulis S
Publication year - 2002
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.832
Subject(s) - curing (chemistry) , polyester , maleic acid , differential scanning calorimetry , styrene , materials science , polymer chemistry , isothermal process , catalysis , activation energy , order of reaction , maleic anhydride , kinetics , copolymer , organic chemistry , chemistry , polymer , reaction rate constant , composite material , quantum mechanics , thermodynamics , physics
Unsaturated polyesters were synthesized based on ethylene glycol and maleic acid as unsaturated dicarboxylic acid, using a variety of saturated acids in the initial acid mixture, without or with different catalysts. The curing of the polyesters produced with styrene was studied using differential scanning calorimetry (DSC) under dynamic‐ and isothermal‐heating conditions. The FTIR spectra of the initial polyesters and cured polyesters were also determined. Curing is not complete at the end of DSC scan and the unreacted bonds were quantitatively determined from the FTIR spectra and by estimation based on literature data. The value of the mean degree of conversion (α) of all double bonds (styrene unit and maleate unit) was approximately α = 0.40. Using an appropriate kinetic model for the curing exotherm of polyesters, the activation energy ( E a ), the reaction order ( x ) and the frequency factor ( k o ) were determined. Because the kinetic parameters (ie E a , k , x ) affect the kinetics in various different ways, the curves of degree of conversion versus time at various isothermal conditions are more useful to compare and characterize the curing of polyesters. The kinetic parameters are mainly influenced by the proportion of maleic acid in the polyesterification reaction mixture and secondarily by the residual polyesterification catalyst. The degree of conversion of already crosslinked polyesters is greatly increased by post‐curing them at elevated temperature and for a prolonged time. © 2002 Society of Chemical Industry