Effect of SiC whisker on benzoxazine‐epoxy‐phenolic ternary systems: Microwave curing and thermomechanical characteristics

Abstract

Microwave radiation at 2.45 GHz with variable power input was investigated as a tool to facilitate the curing reaction of benzoxazine-epoxy-phenolic molding compound i.e., BEP893. Dielectric filler for microwave coupling was silicon carbide whisker (SiC w ). Factors such as whisker loading and input irradiation power were found to have a profound effect on the microwave heating of the BEP893 particularly on the rate of temperature rise and maximum heating temperature. The SiC w loading of 10% by weight with the microwave irradiation condition of 300 W for 10 min renders the ultimate curing of the molding compound. Significant reduction in processing time of the microwave cured sample compared with the conventional heat cured sample i.e., 150 min at 2008C using conventional heating is the key benefit of this technique. Mechanical properties of the microwave cured and conventional heat cured samples show similar characteristics with slightly lower T g in the microwave cured samples.

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

“…1. All of the cured BEP polymer systems showed only single T g implying the miscibility of the benzoxazine, epoxy and phenolic novolac resins [17,19,31]. As can seen in the thermograms, T g s of the samples possess a T g of 1558C which is close to that of the neat polybenzoxazine about of 1608C [8,14].…”

“…However, the incorporation of substantial amount of epoxy resin in the BEP mixtures results in increase of the dielectric constant that should enhance the microwave coupling capability of the resulting mixtures due to the outstanding microwave coupling capability of the epoxy resin. This finding can be attributed to its relatively polar nature of the resin and make it one of the most investigated resins for processing by microwave [19,20]. Figure 7 illustrates the dynamic mechanical characteristics of the fully cured BEP composite systems filled with 10 wt% of SiCw and processed by conventional heating.…”

“…Furthermore, the ability of benzoxazine resin to blend with other polymers or resins [8][9][10][11][12][13][14][15][16] provides the resin with even broader range of applications. The hybrid systems based on benzoxazine, epoxy, and phenolic resins are of particular interest in this study as the systems show synergistic behavior in some of their properties in addition to their excellent processability such as low viscosity, void-free, fast curing at relatively broad range of processing temperature depending on the resin composition and high reliability of the cured samples [12,[17][18][19]. In general, benzoxazine fraction in the ternary systems is found to provide thermal stability, higher char yield, reduction in thermal expansion while liquid epoxy was used as a reactive diluent as well as crosslink density enhancer in the ternary systems.…”

“…They found that dielectric constant value of ABS polymer, i.e., 1.5-2.5; can be improved over 8 with an addition of barium titanate about 30% by volume into ABS polymer. Recently, ceramic whiskers have been used extensively as reinforcement materials in polymer matrix composites to improve mechanical performance under demanding applications [19,[31][32][33]. One of most developed and commercialized ceramic whisker is based on silicon carbide (SiC w ).…”

“…The much faster curing time of the microwave-treated sample compared with the traditional heat-cured molding compound is the key benefit of this technique while the mechanical and thermal behaviors of the SiC w -filled polybenzoxazine showed no significant difference from each other with either of curing methods. In another previous work, the effect of sili-con carbide whisker content on microwave processing and thermal properties of the ternary systems based on benzoxazine, epoxy, and phenolic resins i.e., BEP893 has been thoroughly studied [19]. Increasing silicon carbide whisker content was reported to enhance the microwave coupling ability i.e., higher composite dielectric constant, of the molding compound with significantly lower power or energy input and a much faster curing time.…”