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

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

RSC Advances

RSC

Año: 2016 vol. 6 p. 88647 - 88655

Thermosetting polymers were synthesized from a commercial epoxy resin (diglycidyl ether of bisphenol A, DGEBA) and atricarboxylic (citric, CA) and different dicarboxylic (sebacic, SA and glutaric, GA) acids. Crosslinking of DGEBA-SA andDGEBA-GA systems was achieved by using an epoxy excess that was homopolymerized after consumming all the acidgroups. It was found that the material properties depend on the diacid length and on the epoxy excess and that, with theproper formulation, vitrimers with Tg values ranging from 51ºC to 62ºC, and a high rate of stress relaxation (less than 1h at160ºC to achieve 63% of relaxation) could be obtained. Notably, using a mixture of tri-functional CA with SA allowed toreduce the epoxy excess while keeping a high Tg value and speeding up the stress relaxation. Three of the formulationswere 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 differentpermanent and temporary shapes on a thermosetting polymer obtained from widely availabl e and affordable rawmaterials.