Anhydride and diamine epoxy–Kevlar composites: thermal and dynamic‐mechanical properties

Abstract

Differential scanning calorimetry (DSC) and dynamic–mechanical thermal analysis techniques have been used to characterize different Kevlar–epoxy composites. Tetrafunctional 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 and final thermal properties depending on epoxy matrix type. As Kevlar content increased DSC heat flow curves shifted to much lower temperatures in the anhydride matrix case, while there was very little difference in the diamine–epoxy one. A significant decrease in the glass transition temperature (Tg) was observed as Kevlar content increased when anhydride matrix was used, while little change was observed in the reinforced diamine systems. Loss tangent and storage modulus versus frequency master curves were obtained from isothermal scans. The main dynamic–mechanical relaxation and its evolution versus frequency with fiber addition was studied. An important shift to high frequencies was observed in the anhydride system. Copyright © 1999 John Wiley & Sons, Ltd.