Issue 77

N. Boychenko et alii, Fracture and Structural Integrity, 77 (2026) 207-216; DOI: 10.3221/IGF-ESIS.77.12

Bio-oils can be introduced into the epoxy system by mechanical mixing, which is one of the simplest methods for modifying epoxy compositions. However, during the modification process, it is crucial to achieve uniform distribution of the modifier throughout the epoxy polymer volume. This can be accomplished by the following methods: • Mixing the components after pre-heating the bio-oils; • Mixing the components after pre-heating the bio-oils with acetone pretreatment [10]. In this study, the mixture of ED-20 epoxy resin and purified bio ‑ oils was subjected to acetone pretreatment. As demonstrated in [10], such treatment reduces the viscosity and improves the homogeneity of the mixture, makes the reactive hydroxyl (–OH) groups of the bio ‑ oil more accessible for subsequent reaction with epoxy groups, and ultimately allows a significant increase in the substitution ratio of epoxy resin by bio ‑ oil without substantial deterioration of the mechanical properties of the composition. Mechanical analysis The mechanical performance of the modified epoxy systems was evaluated under tension, three-point bending, and compression tests conducted in accordance with ISO 527-2, ISO 178, and ISO 604, respectively. For each composition listed in Tab. 1, five specimens were tested under each loading type. Specimens were tested to failure in tension and bending, while compression tests were carried out until peak load attainment.

a c Figure 1: Specimen configurations for: (a) tension, (b) three-point bending, (c) compression testing b

Test specimens were fabricated by casting the prepared epoxy systems into silicone molds pre-treated with a release agent. The geometries and dimensions of the test specimens were established according to applicable standards and are shown in Fig. 1. Following demolding, the samples were thermally cured in an oven using the method described in [24]. After curing, the specimens were ground to remove casting defects. Images of the final specimens are presented in Fig. 2.

a c Figure 2: Fabricated specimens for: (a) tension, (b) three-point bending, (c) compression testing Mechanical testing was performed using an LDS-5L universal electro-mechanical testing system (Jinan Liangong Testing Technology Co., Ltd., China). b

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