Anhydride and diamine epoxy-Kevlar composites: Thermal and dynamic-mechanical properties

Differential scanning calorimetry (DSC) and dynamic-mechanical thermal anal ysis techniques have been used to characterize different Kevlar-epoxy compo sites. Tetra-functional aliphatic amine and anhydride-diglycidyl epoxy have been used as matrix, and different quantities of continuous Kevlar fibers as reinforcement. Kevlar fibers had different effects on curing kinetics an d final thermal properties depending on epoxy matrix type. As Kevlar conten t increased DSC heat flow curves shifted to much lower temperatures in the anhydride matrix case, while there was very little difference in the diamin e-epoxy one. A significant decrease in the glass transition temperature (T- g) was observed as Kevlar content increased when anhydride matrix was used, while little change was observed in the reinforced diamine systems. Loss t angent and storage modulus versus frequency master curves were obtained fro m isothermal scans. The main dynamic-mechanical relaxation and its evolutio n versus frequency with fiber addition was studied. An important shift to h igh frequencies was observed in the anhydride system. Copyright (C) 1999 Jo hn Wiley & Sons, Ltd.