Research report: External-catalyst-free transcarbamoylation in hydroxyurethane-modified epoxy vitrimer: enabling ultra-tough, rapidly welding, and self-healing carbon fiber/epoxy composites

A laboratory polymer study has found that a catalyst-free hydroxyurethane-modified epoxy vitrimer can combine high mechanical strength with scratch healing, thermal repair and repeated reprocessing. The researchers created a fully aliphatic hybrid network that undergoes thermally activated transcarbamoylation, allowing covalent bonds to rearrange without an external catalyst. In the cured matrix, tensile strength reached 75 MPa, flexural strength 112 MPa, fracture toughness 3.6 MPa m 1/2 and fracture energy 2.9 kJ/m 2 .

Microscopic analysis showed complete closure of scratches after heating, providing visual evidence of self-healing in the tested samples. The material was synthesized by reacting isophorone diamine with 1,4-butanediol bis(glycidyl ether carbonate) to produce amine-terminated hydroxyurethane prepolymers. Those prepolymers served as curing agents for a matrix based on trifunctional trimethylolpropane triglycidyl ether.

Its defining feature is the network’s capacity for bond exchange: at elevated temperatures, transcarbamoylation permits the cross-linked structure to rearrange while retaining its covalent framework. Stress-relaxation analysis gave a relaxation time of 28 seconds at 200 °C, indicating rapid network rearrangement under that measurement condition. Reprocessing tests demonstrated that ground and hot-pressed specimens could recover much of their original performance.

The material retained 91% of its original tensile strength, 87% of its flexural strength and 85% of its fracture toughness after this treatment. Carbon-fiber composites made with the matrix initially reached a tensile strength of 607 MPa, flexural strength of 691 MPa and interlaminar shear strength of 53 MPa. According to the study, the reinforced composites also retained mechanical integrity through three thermal-repair and recycling cycles, supporting their potential for use in structures intended for multiple service lives.

These results are based on laboratory specimens and do not establish performance in a full-scale structural application. Repair and reprocessing in the reported experiments depended on heating, including a stress-relaxation test conducted at 200 °C, while the supplied findings do not quantify long-term aging, impact damage, moisture exposure or performance under sustained service loads. The measured combination of mechanical performance, complete scratch closure, rapid stress relaxation and partial property recovery after reprocessing suggests that catalyst-free transcarbamoylation could support more durable composite designs, although broader application-level validation remains necessary.

Subject of Research: Catalyst-free hydroxyurethane–epoxy vitrimers for tough, self-healing and recyclable carbon-fiber composites

Article Title: External-catalyst-free transcarbamoylation in hydroxyurethane-modified epoxy vitrimer: enabling ultra-tough, rapidly welding, and self-healing carbon fiber/epoxy composites

Article References: Pouladvand, A. R., Beheshty, M. H., & Yeganeh, H. (2026). External-catalyst-free transcarbamoylation in hydroxyurethane-modified epoxy vitrimer: enabling ultra-tough, rapidly welding, and self-healing carbon fiber/epoxy composites. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13868-5

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13868-5

Keywords: vitrimers, epoxy composites, carbon fiber, self-healing polymers, transcarbamoylation, dynamic covalent chemistry, thermal repair, recycling, fracture toughness, hydroxyurethane, External-catalyst-free, hydroxyurethane-modified