Thermal and mechanical characterization of amine-epoxy/Kevlar fibre composites

Experimental results of dynamic-mechanical: measurements and differential s canning calorimetry are compared for a pure diglycidyl-type epoxy/tetrafunc tional aliphatic amine system and for a composite containing Kevlar fibres as reinforcement. The presence of fibres had marked effects on the curing r eaction, depending on the curing temperature. At low curing temperatures, t he extent of the reaction was lower for reinforced than for neat formulatio ns. For higher curing temperatures, the thermograms shifted to shorter time s as the fibre content increased. In dynamic curing, an increase in the fib re content affected the curing kinetics by slightly shifting the heat flow curves to higher temperatures, and resulted also in a reduction of the glas s transition temperature of the matrix if postcuring was not applied. The d ependence of the dynamic-mechanical spectra of the samples on fibre content was satisfactorily modelled with the aid of Takayanagi's block model. An a nalysis of the main relaxation master curve shows that relaxation broadens as fibre content increases. (C) 1999 Society of Chemical Industry.