Shape memory epoxy vitrimers based on waste frying sunflower oil

Thermoset polyesters are prepared from epoxidized waste frying sunflower oil (ESO), commercially available epoxy compounds and glutaric acid. Influence of the nature and concentration of bi- and trifunctionnal epoxy compounds on mechanical properties is studied. Static and dynamic mechanical tests are performed. The molar amount of commercial epoxy compounds used ranges from 20% to 80% regarding the molar amount of ESO. It enables to obtain thermosetting polyesters with glass transition temperatures ranging from 6 degrees C to 102 degrees C, as well as storage modulus ranging from 8 GPa to 14 GPa. 40% of trifunctional epoxy compound and 60% of commercial epoxy compound are found to be the best compromises between bio-based content and mechanical properties. Furthermore, shape memory and vitrimer behavior of those epoxy-acid based networks with 60% of commercial epoxy compounds are evaluated both qualitatively and quantitatively by cyclic thermo-mechanical and stress relaxation tests. Excellent shape memory behavior with fixity ratios above 94% and recovery ratios above 98% is demonstrated. A transesterification catalyst is needed to obtain good vitrimer behavior. Overall, thanks to the previously mentioned properties of those partially biobased thermosets polyesters, industrial applications such as protective coatings, foams and temperature-memory polymer actuators might be considered.

Automated summary

Thermoset polyesters were prepared from epoxidized waste frying sunflower oil, commercially available epoxy compounds, and glutaric acid. The study focused on the influence of bi- and trifunctional epoxy compounds on mechanical properties, with the best compromise found to be 40% trifunctional and 60% commercial epoxy compounds. The resulting polyesters exhibited a wide range of glass transition temperatures and storage modulus, with excellent shape memory behavior demonstrated in networks containing 60% commercial epoxy compounds.