FTIR spectroscopy and physical properties of an epoxy/bismaleimide IPN system

Blends of a tetrafunctional epoxy resin and a thermosetting bismaleimide (B MI) resin cured with 4,4'-diamino diphenyl sulfone were investigated. Infor mation on the conversion of the reactive groups upon curing was obtained by Fourier transform infrared spectroscopy. Dynamic-mechanical tests carried out on both dry and wet samples indicated the formation of an IPN-like stru cture and a considerable reduction of the plasticizing effect of the water absorbed in the presence of BMI. Sorption measurements at 70 degrees C reve aled a reduction of the equilibrium water uptake with respect to the neat e poxy matrix, and a slight increase of the apparent diffusion coefficient. F urthermore, the presence of BMI enhanced such properties as the flexural el astic modulus and the compressive yield stress while reducing slightly the fracture parameters K-lc, and G(lc) (critical stress intensity factor and c ritical strain energy release rate, respectively), as a consequence of the reduced ability of the IPN network to be plastically deformed under loading . (C) 1998 Kluwer Academic Publishers.