Aging in Water and in an Alkaline Medium of Unsaturated Polyester and Epoxy Resins: Experimental Study and Modeling

The change in stiffness with temperature in the presence of different media has been discussed for a long time because the ability to predict this behavior becomes fundamental to the design of new materials and their applications. That is why, in this work, the application of a mathematical model, which is able to predict the elastic properties of two polymers, is presented. The study takes into account the relationship between the viscoelastic and absorption properties of these materials in alkaline solution (Ca (OH)(2), pH 12.5) and in distilled water (H2O, pH 7) as the immersion media. Diffusion coefficient values were higher when the resins were immersed in water than in the alkaline solution. In addition, the effect of the alkaline medium was higher for the unsaturated polyester resin (UPR). The highest decrease in modulus at the glassy state of the polymer network was observed for the UPR immersed in the alkaline medium. The greatest reduction of the T-g value due to network plasticizing was found for the epoxy resin (ER) in the alkaline medium. Therefore, the ER exhibited a more stable behavior after aging at moderate temperature than the UPR.