Graphene oxide (GO) has been successfully used as a filler to modify various properties of polymers and fiber-reinforced composites. The resulting properties depend on the filler content and on the distribution of GO in the polymer matrix. In this work, for the first time, we introduced GO into the highly viscous DEN-438 epoxy novolac resin and investigated rheological properties of the resulting compositions. In particular, we studied the functions of complex viscosity, storage and loss moduli, and mechanical loss tangent on temperature and GO content. The unusual behavior of the newly prepared formulations compared to typical GO/epoxy mixtures was discovered. At low GO content, introduction of GO led not to an increase, but to a decrease in the resin viscosity, with the minimum registered at 0.29 wt.% GO. After this threshold value, viscosity increased with GO content, which we explained by formation of the liquid crystalline structure. At higher GO concentrations, the formulations changed their state from solid-like at rest to liquid-like under load, with the properties being highly desired for film binders. The discovered properties of the GO/novolac epoxy resin formulations suggest their potential use as the new generation of film binders for Resin Film Infusion technology.

RELEVANCE . Epoxy foams produced by thermal expansion of polymer microspheres show promise as sandwich panel cores. During secondary heating of epoxy foams, significant shrinkage or thermal expansion may occur, depending on the foam composition. Research and prediction of these processes is necessary for the design of sandwich products with epoxy foam cores. THE PURPOSE . To study the thermal expansion and shrinkage of epoxy foams during secondary heating. To estimate the pressure created in a confined tooling space due to expansion. METHODS . Dynamic mechanical analysis was used to estimate the glass transition temperature of epoxy foams. The foaming process of microspheres was studied using thermomechanical analysis. Thermal expansion and shrinkage were assessed by measuring the linear dimensions and volume of the foam before and after heat treatment. The pressure during the thermal expansion of foam plastics was assessed using pressure sensors and recorded using the DiamonPlus dielectric composite molding process monitoring system (INASCO). RESULTS . It was shown that secondary heating of epoxy foam plastics can cause shrinkage or expansion of the material depending on the microsphere content. Thermal expansion pressure increases with increasing foam plastic density. CONCLUSIONS . The temperature conditions for secondary heat treatment were selected, and thermal expansion studies were conducted for epoxy foam plastics with different microsphere contents and initial densities. It was shown that the initial minimum foam density decreases, while the density after heat treatment increases with increasing microsphere concentration. With an increase in the initial foam plastic density at a constant microsphere concentration, the foam plastic density after heat treatment decreases. For foam plastics with a high initial density and a high microsphere content, anisotropy of expansion and contraction after heat treatment is observed.

The paper considers the possibility of using aluminosilicate binders as a foaming aggregate for sandwich panels. The main factors influencing the foaming process (viscosity, surface tension of the compositions, as well as the time and temperature of the process) are investigated. The optimal foaming temperature and time of drying, foaming, and solidification have been determined to achieve a strong and homogeneous foam structure. Tests for the strength of the glued joint of the obtained panels have been carried out.

The influence of montmorillonite on the polymerization and properties of photocurable resin has been investigated. It has been shown that montmorillonite added to the binder composition does not retard the curing reaction and does not suppress UV curing. Montmorillonite improves the elasticity modulus and does not influence the glass transition temperature of UV-cured compositions.

The benefits and advantages of using 3D gradient printing to create ABS plastic-based layered composites reinforced with carbon fibers (CF) and iron oxide nanoparticles (NP) were studied. Samples with different additive contents, as well as a gradient sample with a gradual change in composition (additive content, wt.%: 30 CF, 15 CF, 0, 5 NP, 15 NP), were 3D printed. The thermophysical, mechanical, and magnetic properties of all samples were determined, and the influence of both qualitative and quantitative composition on them was analyzed. Based on the 3D modeling and the preliminary analysis of interlayer adhesion, the need for an intermediate layer of pure polymer between the layers with CF and NPs was shown. Optimal 3D printing settings were selected, and a part with a gradient composition was manufactured and subsequently used to assemble an industrial robot. Overall, the results reveal that deliberate incorporation of various materials or additives into specific regions of a composite offers a way to realize unique combinations of its mechanical, thermal, and electrical properties, tailored to specific applications.