Preparation and characterization of cyanate/epoxy foam

Abstract

A new type of cyanate (CE)/epoxy (EP) foam with bisphenol-A dicyanate ester prepolymer and diglycidyl ether of bisphenol-A (BADCy/DGEBA) has been successfully prepared through a two-step process. The structure and properties of CE/EP foam were studied. The results reveal that the CE/EP foams, with relatively uniform cell structure, were composed of closed cells as confirmed by scanning electron microscopy. The compressive strength increased from 0.507 MPa to 3.021 MPa, and the compressive modulus ( E) increased from 15 MPa to 123 MPa as the density increased from 0.103 g cm−3 to 0.305 g cm−3. Dynamic mechanical analysis revealed that the CE/EP foams possessed a high glass transition temperature ( Tg) (203°C) and that density had only a little impact on Tg. Moreover, the excellent thermal stability presented with the onset of weight loss taken at 5% value was above 320°C, and the residual weight of the foam was more than 21.6% at 800°C. With increase in the density of CE/EP foams, the dielectric constants (ε) gradually decreased. For the foam with density of ρ = 0.162 g cm−3, the value of ε was as low as 2.28 at the frequency of 10 kHz.