Tung Oil-Derived Epoxy Vitrimers with High Mechanical Strength, Toughness, and Excellent Recyclability
Laihui Xiao, Wenbin Li, Zengshe Liu, Kun Zhang, Shuai Li, Yigang Wang, Jie Chen, Jinrui Huang, Xiaoan Nie
Abstract
The application of diglycidyl ether of bisphenol A (DGEBA) is severely limited due to the poor toughness of its thermosets, and the growing concern for sustainability calls for materials with recyclability. Thus, two tung oil-based compounds (DA-MA and TA) with different contents of carboxylic acid and anhydride were prepared and used to cure DGEBA to fabricate vitrimers, a kind of thermoset cross-linked through reversible covalent bonds. Test results show that vitrimers derived from tung oil (EP-DA-MA and EP-TA) exhibit excellent mechanical strength and toughness. In particular, the tensile strength, elongation at break, bending strength, bending toughness, and impact strength of EP-DA-MA are 63.17 MPa, 5.34%, 92.96 MPa, 1.09 kJ·m–2, and 7.73 kJ·m–2, respectively, while these parameters of the control, DGEBA cured with commercial methyl nadic anhydride, are 60.86 MPa, 1.77%, 78.94 MPa, 0.14 kJ·m–2, and 4.42 kJ·m–2. Meanwhile, high content of reversible ester bonds and secondary hydroxyl groups may facilitate the transesterification in the recycling process; thus, the crushed vitrimers of EP-DA-MA and EP-TA can be remolded without additional catalysts, and the tensile strength of the recycled samples can reach almost 100% of the original sample size, suggesting excellent malleability and recyclability. Therefore, the tung oil-derived epoxy vitrimers are promising candidates for utilization as adhesives, coatings, and matrix resins.