The effect of nano-gelcoat on freeze-thaw resistance of glass fiber-reinforced polymer composite for marine applications

Glass fiber-reinforced polymers and protective gelcoats are important construction materials used in marine structure engineering. This study focused on the effect of freeze-thaw test on the properties of glass fiber-reinforced epoxy composites coated with nano-gelcoat. Nanoclay and nano TiO2 (1, 2, 3 wt%) were used to prepare nano-gelcoat and applied to composite surfaces. After the 45 and 90 freeze-thaw cycles, the change in the mechanical properties of the composites was determined and the thermal stability of the coatings was investigated. Mechanical features were investigated by tensile, flexural, short beam and compression tests. The thermal stability of the gelcoats was determined using Differential thermal analysis (DTA) and Thermogravimetric analysis (TGA). The morphology of the coatings was investigated by SEM (Scanning electron microscope). Water absorption properties were tested in hydrothermal environment. Finally, a statistical analysis, ANOVA (Analysis of variance), was conducted to determine whether the experimental results were significant or not. Nano TiO2 improved the water absorption property by 15.09% and preserved the mechanical properties by up to 8.8% compared to pure gelcoat. Nano TiO2 increased the melting temperature from 224.46 °C to 261.59 °C and provided a 16.54% improvement and also increased the decomposition temperature. Since the thermal conductivity of nanoclay is higher than nano TiO2, the nanoclay contribution increased this value by 7.14% and the nano TiO2 contribution by 3.57%. However, nanoclay has reduced the protection property of pure gelcoat due to its shape and size disadvantages. ANOVA analysis also revealed that the results were statistically significant. [Display omitted] •Glass fiber reinforced epoxy composite were coated with nanogelcoat produced using nano TiO2 and nanoclay.•The change in mechanical and thermal properties were investigated after conducting freeze/thaw test.•Nano TiO2 increased the protection property of pure gelcoat while nanoclay decreased it.•Nano TiO2 preserved the mechanical property up to 8.8% and improved melting point up to 16.54% compared to pure gelcoat.•The results were statistically significant according to the ANOVA analysis.