New aromatic-aliphatic hyperbranched polyesters with vinylic end groups of different length as modifiers of epoxy/anhydride thermosets

The synthesis and characterization of two new aromatic-aliphatic hyperbranched polyesters modified with long and short vinylic chains was reported. These hyperbranched polymers were used as toughening modifiers of epoxy/anhydride thermosets. The curing of mixtures of diglycidyl ether of bisphenol A and hexahydro-4-methylphtalic anhydride with different proportions of both hyperbranched polymers using N,N-benzyldimethylamine as catalyst was investigated by differential scanning calorimetry. The kinetic of curing process was established using an isoconversional integral procedure. The characterization of these materials was done by means of several thermal analysis techniques and their morphology was investigated by electron microscopy. The addition of highly branched structures led to homogeneous morphologies and a more toughening fracture of the thermosets in comparison to the neat epoxy/anhydride material. The modified thermosets presented slightly lower glass transition temperature than the unmodified one and the thermal stability barely changed by the addition of the modifiers. (c) 2012 Elsevier Ltd. All rights reserved.