Optimizing mechanical and thermomechanical properties of the self-healable and recyclable biobased epoxy thermosets

Recently, biobased high-performance vitrimers have been developed due to the lacking of raw materials from petroleum resources that can be processable as like thermoplastic to meet the urgent demand for sustainable development. Herein, the fully biobased imine curing agent (VBI-HMDA) was synthesized from bio-resources vanillin and hexamethylenediamine and its chemical structure was ensured in detail through FTIR, H-1-NMR and C-13-NMR before being cross-linked by commercially available Diglycidyl ether of Bisphenol-F (DGEBF). Cyclic 4-methyl-1,3-cyclohexendiamine (HTDA) was used as a co-curing agent with VBI-HMDA at different weight ratios in terms of improving the properties of cured thermoset. The curing behaviors, mechanical, thermal and self-healing performance of the cured thermosets were investigated by DSC, strength tester, DMA and TGA analyzer. However, the viscosity and activation energy of curing are decreased as the weight ratio of HTDA increases, while flexible properties and T-g values are increased gradually. In addition, the heat-resistant temperature (T-s) and char residue at 700 degrees C of the cured thermosets also decreased. Overall results of 50% containing HMDA sample S03 exhibited the utmost thermomechanical performances as well as admirable self-healing ability and processability. Moreover, the recycling property of S03 is over 74%, T-g of reprocessed S03 is still as high as 99 degrees C and it is entirely solvent resistant at room temperature. This result suggests the optimizing mechanical and thermomechanical properties of cured thermosets with potential recyclability were efficiently controlled by adjusting the co-curing agent ratio.