Thermal and Moisture Adsorption Properties of Cyanate Ester Modified Epoxy Resin and Fiber-Glass Composites

The moisture absorption and heat distortion temperature (HDT) of cyanate ester modified epoxy resin in various resin blend ratio and cure conditions were studied. The experimental results showed that the moisture concentrations of 180°C-cure products were lowest and the HDT of 200°C-cure products were highest in co-cure systems with cyanate ester's weight fraction of 30, 40, and 50%. If all of the samples were post-cured at 230°C for 4h, the moisture concentration and HDT of samples with the same content of cyanate ester in the blend were very approximate. This indicated that the post-curing temperature was an important factor affecting thermal properties and moisture absorption. Fourrier transform infrared (FT-IR) was used to analyze the structure of products and to discuss the change of moisture absorption and HDT. In addition, the order of the effect of every factor, cyanate ester content, accelerant (cobalt isocaprylate) content, cure time, and cure temperature, on moisture absorption and HDT, were found out by an orthogonal test. The optimal conditions for preparing lowest moisture concentration and highest HDT product were determined respectively. A dynamic mechanical thermal analyzer (DMTA) was used to detect the changes of the glass transition temperature (Tg). All of the dynamic mechanical loss tangent cures of composite have two glass transition peaks. The shape of these two peaks changes with increasing immersing time, but the corresponding temperature of peak value changes little.