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A new strategy for controlling shrinkage of DGEBA resins cured by cationic copolymerization with hydroxyl‐terminated hyperbranched polymers and ytterbium triflate as an initiator
Author(s) -
FernándezFrancos Xavier,
Salla Josep Maria,
Cadenato Ana,
Morancho Josep Maria,
Serra Angels,
Mantecón Ana,
Ramis Xavier
Publication year - 2008
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.29317
Subject(s) - diglycidyl ether , differential scanning calorimetry , cationic polymerization , thermogravimetric analysis , materials science , epoxy , thermosetting polymer , glass transition , curing (chemistry) , thermal stability , polymer chemistry , copolymer , trifluoromethanesulfonate , polymer , composite material , bisphenol a , chemistry , organic chemistry , catalysis , physics , thermodynamics
We report a novel strategy for preparing epoxy thermosetting systems with low shrinkage and improved flexibility and degradability. Diglycidyl ether of bisphenol A (DGEBA) resin was cured with different proportions of hydroxyl‐terminated hyperbranched polymer (HBP), using ytterbium triflate as a cationic initiator. The curing process was studied using differential scanning calorimetry and thermomechanical analysis. Characterization of the resulting materials was evaluated using DSC, thermogravimetric analysis, and dynamic mechanical thermal analysis, and the fracture surface was studied using scanning electron microscopy (SEM). When DGEBA is modified with HBP, it shows a homogeneous morphology and the HBP is incorporated chemically into the network, because hydroxyl groups can react with epoxides under cationic conditions. Higher proportions of HBP reduce the glass transition temperature ( T g ) and thermal stability and increase the flexibility. When the proportion of HBP in the curing mixture is increased, the degree of shrinkage is reduced significantly and expansion can be observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009