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Moisture diffusion was studied through vinyl ester samples containing up to 5 wt% of organically treated montmorillonite. Two different kinds of clay surface treatment were employed to make the clay compatible with DerakaneTM 411‐350 vinyl ester resin. The nanocomposites were characterized using differential scanning calorimetry (DSC), mechanical property measurements, X‐ray diffraction (XRD) and transmission electron microscopy (TEM). TEM pictures showed that the clay platelets were either exfoliated or intercalated, and the two different surface treatments resulted in different dispersion characteristics. All the samples were post cured, and the diffusivity of moisture was measured by soaking the samples in 25°C water and noting the increase in weight with increasing time of immersion. It was found that water diffusivity decreased with increasing clay content, and it was reduced to half its value in the neat resin when the clay content was only 1 wt% regardless of the nature of clay surface treatment. However, the equilibrium moisture content, the glass transition temperature, and the elastic modulus all increased with increasing amounts of clay.

This article presents recent developments in long-term behavior of fiber-reinforced polymer composites subjected to moisture, pH, temperature, sustained stress and ultraviolet radiation, as well as response under combined effects of moisture, pH, etc. Although numerous experiments have been conducted to investigate the durability of fiber-reinforced polymers under different environments, at this stage, it is difficult to ascertain the degradation trends and mechanisms of failures of fiber-reinforced polymers because of non-standardization of various conditioning effects and variation in material constituent. Recent findings on the long-term performance of fiber-reinforced polymer composites are synthesized herein. This article critically examined not only the moisture uptake response, mechanical property and failure modes of fiber-reinforced polymers under varying environments, but also the degradation mechanism through physical and chemical reactions. Moreover, based on information in literature, long-term predictive models were described along with the application potential and limitations. The strength reduction factors were proposed from available data to account for the environmental effects on fiber-reinforced polymers.

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