Effects of oxidation and silanization on the durability and tensile properties of carbon nanotube‐reinforced vinyl‐ester nanocomposites

Abstract Carbon nanotubes (CNTs) have received significant attention due to their exceptional physical and mechanical properties. Advancements in surface modification techniques have facilitated their use in thermoset resin‐based nanocomposites, enhancing engineering properties with minimal additions (0.1 wt.%). This study investigated the effects of various functionalization methods of multi‐walled carbon nanotubes (MWCNTs) on the mechanical, physical, durability, and moisture absorption properties of vinyl‐ester resin (VE). While VE resins resist short‐term environmental degradation, prolonged exposure to moisture and alkaline chemicals can lead to deterioration. To overcome this challenge, MWCNTs were modified using wet acid oxidation, silanization (both with and without prior oxidation), and a zirconate coupling agent (SM7SN). Modifications were characterized using scanning electron microscopy (SEM) and x‐ray photoelectron spectroscopy (XPS). The tensile test and dynamic mechanical analysis (DMA) were performed on the specimens before and after conditioning in NaOH solution. Moisture absorption was measured by immersing the specimens in tap water at 50°C. The results showed that pre‐oxidation of MWCNTs before silanization significantly enhanced silane attachment and improved the durability of the nanocomposites, with a negligible reduction in mechanical properties after conditioning. Using SM7SN as a dispersing agent significantly improved matrix properties and offered a simpler modification method compared to other techniques. Highlights Covalent and non‐covalent methods improved CNT dispersion in VE matrix. Pre‐oxidation before silanization enhanced Si‐O‐C bonds. SEM and XPS confirmed successful CNT functionalization and dispersion. Functionalized CNTs reduced the moisture absorption of nanocomposites. SM7SN agent ensured uniform dispersion and simplified CNT modification.