Evaluation of the post cure use on the thermal and mechanical properties of a room temperature curing epoxy system
ABSTRACT In this work, a room temperature curing epoxy system was submitted to post cure cycles to evaluate the thermal and mechanical properties of the material. The samples were obtained by casting into a metallic tool and the post cure cycles were performed at 75°C, 90°C, 110°C for one hour and at 110°C cycle for 2 hours. The differential scanning calorimetry (DSC) results showed that the glass transition temperature of the material have not change significantly with the post cure cycles, which indicates a number of molecular crosslinks very similar to the original sample, without post cure. The thermogravimetric (TGA) results revealed a stepwise thermal degradation; where about 70% mass of the material undergoes thermal degradation in the temperature range from 330.9°C to 345.1°C. The temperature-time transformation (TTT) diagram of a thermoset polymer was used to understand the cure kinetics, where it was suggested that the amount of resin and curing agent had a more significant influence on the full curing of the sample than the post cure cycles carried out in this article. By means of mechanical properties, the hardness of the material remained unchanged with the post curing cycles. Only one batch obtained lower values of hardness because the excess of curing agent worked as plasticizing agent. O In terms of elastic modulus, the free-beam method presented values between 1.72GPa and 2.18GPa, and the post cure cycles did not have any notable influence on this property.