# The Influence of Copper Oxide Particle Size on the Properties of Epoxy Resin
## 1 Introduction
The elongated silica mineral particles demonstrated higher flexural strength and tensile properties, as well as a comparable coefficient of thermal expansion, compared to composites with fused silica-based fillers, features attributed to the higher aspect ratio of the elongated particles and thus a stronger bond between the resin and the filler [15]. In their work, [PERSON] et al. examined the influence of the particle size and content of silicon carbide particles in an epoxy matrix on the mechanical properties of epoxy composites. The study investigated the effects of particle sizes of <45 \(\upmu\)m and 90-45 \(\upmu\)m and tested densities of 2, 4, 6, and 8 wt%. SiC. The results revealed a strong negative correlation between hardness and flexural strength, as well as a positive correlation between hardness and the flexural modulus and between compressive stress and the compressive modulus. The test results also indicated that the addition of smaller silicon carbide particles (<45 \(\upmu\)m) resulted in excellent mechanical properties in terms of bending and compression and hardness test results. Furthermore, it was observed that an increase in SiC particle content led to a decrease in flexural strength, while compressive strength and hardness increased with increasing particle loading [16]. [PERSON] et al. investigated the influence of extremely small SiC particles on the nano- and microscales, using particle contents of 6% and 12%. The results showed that the incorporation of silicon carbide decreased the glass transition temperature Tg due to a reduction in cross-linking points. This effect was less pronounced when using nanoscale particles. The mechanical test results revealed heterogeneity attributed to the non-uniform distribution and agglomeration of nanoparticles in the composite, as well as problems with wettability leading to material porosity. However, it was clearly demonstrated that nanoparticles increased the material's plasticity when \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Properties**} & \multicolumn{3}{c}{**Type of Resin**} \\ \cline{2-4}  & **Polyseter** & **Vinylester** & **Epoxy** \\ \hline Density, g/cm\({}^{3}\) & 1.23 & 1.04 & 1.14 \\ \hline Tensile strength, MPa & 70 & 85 & 75 \\ \hline Modulus of elasticity, GPa & 3.8 & 3.3 & 3 \\ \hline Elongation at break, \% & 2.3 & 5 & 5 \\ \hline Thermal expansion coefficient, 6–10/\({}^{\circ}\)C & 80–160 & 65 & 80–120 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of selected properties of thermosetting resins. Adapted with permission from Ref. [8]. 2013, Taylor & Francis Online and from Ref [9]. 2022. [PERSON]. bending. Additionally, 6% nano-SiC significantly reduced die wear. Microparticles were found to be an effective additive for increasing the strength of the composite, but they decreased wear resistance [17]. [PERSON] et al. investigated the influence of fiber reinforcement and macro- and microparticles of banana on the characteristics of epoxy resin, focusing on the properties of tensile strength, bending strength, impact strength, and hardness. The study involved testing composite materials with different additive contents ranging from 25 to 35% by weight. The outcomes of the tests revealed that while fibers contributed to the highest tensile strength, the particles led to the greatest increase in the bending modulus. Additionally, both banana fibers and macroparticles were found to enhance impact strength compared to unmodified resin. Furthermore, the mechanical properties of the composites were observed to improve as the additive content of both fibers and particles increased [18]. In his study, [PERSON] analyzed the impact of Al\({}_{2}\)O\({}_{3}\) particles on the characteristics of epoxy-glass composites. The Al\({}_{2}\)O\({}_{3}\) content in the composites was between 2% and 15% by weight. The findings revealed that the tensile strength and shear strength of the composites significantly decreased as the Al\({}_{2}\)O\({}_{3}\) content increased.