## 2 Materials and Methods
### Characterization and Measurement  
Thermogravimetric analysis (TGA) was performed on NETZSCH TG 209 F1 Libra (Selb, Germany) within a temperature range of 30 to 550 C at a heating/cooling rate of 10 K min-1 in an argon atmosphere. The method of differential scanning calorimetry (DSC) (NETZSCH DSC 204 F1 Phoenix, Selb, Germany) was used to determine the thermal characteristics of binders in the measurement temperature range of 15-200 C, with a heating rate of 10 K/min-1 in argon atmosphere. DMA measurements were carried out according to a three-point loading scheme on a DMA 242 E Artemis analyzer (Netzsch, Selb, Germany) at a temperature of 30 C. The load application frequency was: 0.25; 0.5; 1.0; 3.3; 10.0 Hz. The CFRP samples were plates 30 mm long, 7 mm wide, and 2 mm  
Figure 1: Synthesis of epoxyfuran oligomer FuEp. thick. The distance between the supports is 20 mm. During the measurement, the value of the modulus of elasticity E' was determined. The measurements were performed in three stages. At the first stage, the elastic modulus E' of the original samples (without notch) was determined, which were obtained after curing. Then, cracks were set at the ends of the sample at 0.5 (i.e., for sample length \(l_{\mathrm{s}}\) = 30 mm and crack length \(l_{\mathrm{c}}\) = 15 mm, ratio \(l_{\mathrm{c}}\)/\(l_{\mathrm{s}}\) = 0.5) and 0.25 (\(l_{\mathrm{c}}\)/\(l_{\mathrm{s}}\) = 0.25), of its length, and E' was measured under the same conditions as in the first stage. At the third stage, the measurements were carried out after heat treatment (self-healing cycle) at 120 \({}^{\circ}\)C for 25 min and 80 \({}^{\circ}\)C for 24, 48, and 72 h. The degree of self-healing of the CFRP was calculated as the ratio of the modulus of elasticity after heat treatment of the notched sample to the modulus of elasticity of the initial (intact) sample. Before heat treatment, it was necessary to bring the surface of the applied crack into contact. For that purpose, force was applied to the samples using clamps (Figure 1). The samples were wrapped in a Teflon film to avoid contact and possible sticking together, and then (Figure 1(3)) they were clamped between clamps, in which steel corners (Figure 1(2)) and rubber (Figure 1(4)) were installed to evenly distribute the load and to control the set force. To determine the force applied to the samples, the rubber tabs were calibrated with a universal testing machine. For each rubber tab, a diagram of the applied force F versus deformation \(\Delta l\) during compression was recorded. From the obtained diagram, the compression force of the samples was determined by comparing the change in the thickness of the rubber after clamping with the deformation on the obtained curve F vs. \(\Delta l\). Thus, the specified load was about 500 N.  
The \(\mathrm{G_{IR}}\) crack resistance of CFRP was determined on a Zwick/Roell Z100 universal testing machine by splitting a double-cantilever beam. The original plates of carbon plastic were cut so that the Teflon film was in the cutting zone of samples for measuring crack resistance, and this was the initial crack. As a result, two samples were obtained for each binder with a length of 110 mm, a width of 18 mm, and a thickness of 2 mm. Before testing, the initial crack was artificially grown a little. At the edges of the samples, cuts were symmetrically applied at a distance of about 5 mm from the end of the sample. These cuts are necessary to secure the wire loops and to apply the force necessary for crack growth. The speed rate of the clamps during the test was 30 mm/min. The sample was loaded until the crack grew to a length of about 10 mm, after which the sample was photographed to determine the bending angles of the cantilevers \(\alpha_{1}\) and \(\alpha_{2}\) (see Figure 2) and the load was  
Figure 1: Samples clamped in a clamp for heat treatment: 1—clamp for clamping samples; 2—steel corners; 3—samples wrapped in Teflon film; 4—rubber. (**a**) Front view; (**b**) Side view. removed. Then, the loading-unloading cycle was repeated 5-6 times.