Investigation of seawater effects on the mechanical properties of untreated and treated MMT-based glass fiber/vinylester composites

The present investigation is focused on montmorillonite (Cloisite^® Na⁺)-based vinylester/glass fiber composites. In the present study, two types of composites are processed by incorporating 1.0 wt% untreated and treated montmorillonite into vinylester/glass fiber composites and the effect of seawater absorption on their mechanical properties was studied for marine applications. The surface treatment of MMT was performed using 3-aminopropyltriethoxysilane. When montmorillonite clay comes into contact with water, swelling between layers occurs that consequently alters the mechanical properties of the composites. The tensile and bending strengths of the composites before and after seawater absorption were investigated using ASTM methods with a Universal Testing Machine. Chemical and physical changes were studied through X-ray diffraction and Fourier-transform infrared spectroscopy. Thermogravimetric analysis was performed to analyze the effect of seawater absorption on the thermal properties. The morphology of the fractured surfaces before and after seawater absorption was analyzed using FE-SEM. The results show that treated MMT-based composites show better mechanical properties in dry and seawater-absorbed conditions than the untreated MMT-based composites, but the mechanical properties of both composites decrease after seawater immersion.