Effect of resin compositions on microwave processing and thermophysical properties of benzoxazine-epoxy-phenolic ternary systems filled with silicon carbide (SiC) whisker

Abstract

Microwave processing of silicon carbide (SiC) whisker filled ternary systems based on benzoxazine, epoxy, and phenolic resins has been investigated using an industrial microwave apparatus at a fixed frequency of 2.45 GHz. The low viscosity molding compound and void-free cured specimens can easily be obtained from the resin mixtures. Increasing of epoxy mass fraction in the ternary systems provided a better microwave coupling, therefore, a faster curing time and higher conversion under microwave irradiation. However, the greater amount of epoxy resin in the mixture was observed to retard the traditional thermal cure process as seen in the shifting of the exothermic curing peaks to higher temperature. The higher dielectric constant of epoxy resin comparing with the benzoxazine resin can be attributed to the observed phenomenon. Additionally, benzoxazine fraction was found to render a reduction in linear thermal expansion coefficient of the ternary systems. The development of ternary systems yields the polymer systems with high flexibility in resin- curing agent mixing ratios with relatively high T g in the broader range of mixing ratios i.e., BEP451-BEP811. Synergism in glass transition temperature of the ternary systems is also observed with the maximum T g up to 160°C in BEP721. © 2009 Society of Plastics Engineers.