Studies on Epoxy Resins Cured by Cationic Latent Thermal Catalysts: The Effect of the Catalysts on the Thermal,Rheological, and Mechanical Properties

摘要

To investigate the effect of catalysts on the thermal, rheological, and mechanical properties of an epoxy system, a resin based on diglycidyl ether of bisphe- nol-A (DGEBA) was cured by two cationic latent thermal catalysts, N-ben- zylpyraziniumhexafluoro~timonate (BPH) and N -benzylquinoxalinium hexafluoroan- timonate (BQH). Differential scanning calorimetry was used for the thermal charac- terization of the epoxy systems. Near-infrared spectroscopy was employed to examine the cure reaction between the DGEBA and the latent thermal catalysts used. The rheological properties of the blend systems were investigated under an isothermal condition with a rheometer. To characterize the mechanical properties of the systems, fle::ur~, fracture toughness (K_(1c)), and impact tests were performed. The phase mor- phology was studied with scanning electron microscopy of the fractured surfaces of mechanical test samples. The conversion and cure activation energy of the DGEBN BQH system were higher than those of the DGEBNBPH system. 'The cross linking activation energy showed a result similar to that obtained from the cure kinetics of the blend systems. The flexure strength,K_(1c), and impact properties of the DGEBNBQH system were also superior to those of the DGEBNBPH system. This was a result of the substituted benzene group of theBQH catalyst, which increased the crosslink density and structural stability of the epoxy system studied.