HYDROTHERMAL EFFECTS ON THE PHYSICOCHEMICAL PROPERTIES OF PURE AND GLASS-FIBER-REINFORCED POLYESTER AND VINYLESTER RESINS

The effect of aging by immersion in water at 60-degrees-C on polyester and vinylester resins, unreinforced and reinforced with glass fibers, was investigated. Changes in weight, glass transition temperature, se condary relaxations, and storage modulus, as well as loss modulus were measured, and the environmental effects on these parameters were asse ssed. Moreover, the chemical structure changes of the materials during aging were studied by the use of IR spectra. The evolution of the phy sico-chemical and the mechanical properties as a function of the aging time was established. The results indicate the importance of the matr ix morphology, the structure regularity, and the presence of the fiber s on the water diffusion mechanisms, and the thermomechanical properti es through gravimetric changes, DSC, DMA and IR experiments.