Plant oil-based epoxy resins are of great interest due to their ecological and economic necessity. In this study, the relationship between the crosslinking density and the thermo-mechanical properties of tung oil-based epoxy resins was established.

Polyurethane is widely used to toughen epoxy resins due to its excellent comprehensive properties and compatibility. However, some demerits of polyurethanes limit their applications, such as the harsh storage condition of isocyanate-terminated polyurethane (ITPU), the limited amount of ITPU in epoxy resin, and using solvents during the preparation of polyurethane-modified epoxy resins. To address these issues, in this study, we reported a facile and green approach for preparing epoxy-terminated polyurethane (EPU)-modified epoxy resins with different EPU contents. It was found that the toughness of the epoxy resin was significantly improved after the addition of EPU. When the EPU content was 30 wt%, the elongation at break and toughness were improved by 358.36% and 73.56%, respectively. In comparison, the toughening effect of EPU outperformed that of ITPU. Moreover, the high content of EPU did not significantly decrease the glass transition temperature and had little effect on the thermal stability of the epoxy resin.

Bio-based vitrimers present a promising solution to the issues associated with non-renewable and non-recyclable attributes of traditional thermosetting resins, showcasing extensive potential for diverse applications. However, their broader adoption has been hindered by the requirement for catalyst inclusion during the synthesis process. In this study, a cardanol-based curing agent with poly-hydroxy and tertiary amine structures was prepared by a clean synthetic method under the theory of click chemistry. The reaction of a cardanol-based curing agent with diglycidyl ether of bisphenol A formed catalyst-free, self-healing, and recyclable bio-based vitrimers. The poly-hydroxy and tertiary amine structures in the vitrimers promoted the curing of epoxy-carboxylic acid in the cross-linked network and served as internal catalysts of dynamic transesterification. In the absence of catalysts, the vitrimers network can achieve topological network rearrangement through dynamic transesterification, exhibiting excellent reprocessing performance. Moreover, the vitrimers exhibited faster stress relaxation (1500 s at 180 °C), lower activation energy (92.29 kJ·mol⁻¹) and the tensile strength of the recycled material reached almost 100% of the original sample. This work offers a new method for preparing cardanol-based epoxy vitrimers that be used to make coatings, hydrogels, biomaterials, adhesives, and commodity plastics in the future.

Hydrothermal liquefaction is used as a novel method to disrupt cell walls and extract lipids from oleaginous yeast (Rhodosporidium toruloides) in a single step.

Carbon fiber-reinforced composites (CFRCs) derived from thermosetting resins and carbon fibers are widely used in aerospace, civil engineering, and sport equipment. However, CFRCs have an undegradable resin matrix and nondestructive recycling of carbon fibers. To address this dilemma, we prepared readily recyclable, high-performance catalyst-free tung-oil-derived vitrimer and CFRCs from tung-oil-based acid curing agents (named as TTMA) and bisphenol A epoxy resin (DGEBA) or 4,4'-methylenebis (N, N-diglycidylaniline) (TGDOM). DGEBA/TGDOM-TTMA networks with plentiful ester bonds, hydroxyl groups, and tertiary amine without extra catalyst can undergo topological rearrangement of cross-linked networks via dynamic transesterification reactions at high temperature. Thus, the epoxy resin matrix of CFRCs has excellent mechanical property, thermostability, and can be easily reprocessed, self-healed, and degraded at elevated temperatures. TGDOM-TTMA has good stress relaxation properties owing to the high concentrations of hydroxyl and tertiary amine. What's more, carbon fibers can be completely recycled from CFRCs using the ethanolamine via amidation reaction, where the recycled carbon fibers maintained nearly 100% of the mechanical properties from the virgin samples. The theoretical implications of this work lie on offering a sustainable and convenient strategy for designing readily recyclable and high-performance CFRCs.