Effect of Nanoclay Modification and Environmental Exposure on the Mechanical and Surface Properties of Polyester Composites.

This article presents the results of a study investigating the influence of surface-modified montmorillonite nanoclay and environmental exposure on the mechanical and surface properties of composites based on orthophthalic unsaturated polyester resin. A series of samples containing 0.02 to 0.1 wt.% of nanoclay, as well as a reference sample, were prepared. Following synthesis, the samples were incubated for one week in aqueous solutions with pH values of 4, 7, and 9. Mechanical testing included tensile strength, flexural strength, impact resistance, and surface roughness (Ra). Additionally, fracture surface analysis was performed using scanning electron microscopy (SEM) and digital optical microscopy. The effect of the additive on hardness was also assessed, and Fourier transform infrared (FT-IR) spectroscopy was carried out. The results indicated that nanoclay addition increased the material's stiffness (Young's modulus), although higher filler concentrations led to decreased impact strength and flexural performance, likely due to particle agglomeration. Incubation in chemically aggressive environments caused mechanical degradation and significant increases in surface roughness, especially after exposure to neutral and alkaline media. Microscopic observations confirmed the presence of microstructural changes and nanoclay agglomerates in selected samples. The findings confirm that the effectiveness of nanoclay modification depends not only on concentration but also on dispersion quality and the environmental conditions to which the material is exposed.