Shape memory epoxy vitrimers based on DGEBA crosslinked with dicarboxylic acids and their blends with citric acid

ALTUNA, F.I.; HOPPE, C.E.; WILLIAMS, R.J.J.

RSC Advances

Royal Society of Chemistry

Año: 2016 vol. 6 p. 88647 - 88655

Thermosetting polymers were synthesized from a commercial epoxy resin (diglycidyl ether of bisphenol A, DGEBA) and a tricarboxylic (citric, CA) and different dicarboxylic (sebacic, SA and glutaric, GA) acids. Crosslinking of DGEBA-SA and DGEBA-GA systems was achieved by using an epoxy excess that was homopolymerized after consumming all the acid groups. It was found that the material properties depend on the diacid length and on the epoxy excess and that, with the proper formulation, vitrimers with Tg values ranging from 51ºC to 62ºC, and a high rate of stress relaxation (less than 1h at 160ºC to achieve 63% of relaxation) could be obtained. Notably, using a mixture of tri-functional CA with SA allowed to reduce the epoxy excess while keeping a high Tg value and speeding up the stress relaxation. Three of the formulations were selected and their shape memory performance was studied. Good shape fixity and shape recovery ratios (>99%) were obtained, indicating a good shape memory performance overall. These properties can be used to create different permanent and temporary shapes on a thermosetting polymer obtained from widely available and affordable raw materials.