Effect of SiC Whisker on Benzoxazine-Epoxy-Phenolic Ternary Systems: Microwave Curing and Thermomechanical Characteristics Sarawut Rimdusit, 1 Varutrit Jiraprawatthagool, 1 Chanchira Jubsilp, 1 Sunan Tiptipakorn, 1 Takeshi Kitano 2 1 Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand 2 Polymer Centre, Tomas Bata University in Zlı ´n, Zlı ´n 76272, Czech Republic Received 12 December 2006; accepted 27 February 2007 DOI 10.1002/app.26383 Published online 1 May 2007 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Microwave radiation at 2.45 GHz with vari- able 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 cou- pling 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 conven- tional heating is the key benefit of this technique. Mechani- cal properties of the microwave cured and conventional heat cured samples show similar characteristics with slightly lower T g in the microwave cured samples. Ó 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 1968–1977, 2007 Key words: composites; mechanical properties; thermal prop- erties; crosslinking differential scanning calorimetry (DSC) INTRODUCTION Benzoxazine resin (BA) was developed as a high flow, low void resin system with a capability of forming thick samples of either filled or unfilled sys- tems. The resin can be synthesized via a simple and cost-effective solventless technology. 1 In addition, molecular design flexibility of the resin comparable to that of epoxy or polyimide renders wide range of properties of the polymer that can be tailor-made. 2–4 The resin has been shown to possess some useful properties such as ease of processing due to its self- polymerizability upon heating via ring-opening po- lymerization thus giving no volatile by-products. The polymer shows near-zero shrinkage upon poly- merization as well as possesses relatively high T g and good thermal stability. 5–8 Ishida and Rimdusit have reported the use of BA-m type polybenzoxa- zine as a matrix for boron nitride filler to obtain a highly filled composite system with high value of thermal conductivity. 9,10 Recently, highly filled wood composites from BA-a type polybenzoxazine with relatively high modulus comparable to natural wood has also been reported. 11 Those high performance composite properties are attributed to the ability of the low viscosity BA resin to accommodate very high filler loading i.e., up to 75% by volume as well as its good adhesive proper- ties. Moreover, the compatibility of the polybenzoxa- zine with various resins renders a large number of polymer alloys or copolymers covering wide range of properties. 12–21 The hybrid systems based on BA, epoxy, and phenolic resins are of particular interest in this investigation since the systems show syner- gistic behaviors in some of their properties in addition to their excellent processbility and high reliability of the cured samples. 17,18 In this investiga- tion, the well-characterized ternary systems namely BEP893 which is the resin mixture of BA resin (B), epoxy resin (E), and phenolic resin (P) at the mass ratio of 8:9:3 is used as a matrix. The processability as well as the cured properties of the resin has al- ready been reported in our previous work. 17 Microwave energy has been an attractive heating source for material processing due to its capability to interact directly with molecules i.e., by raising their rotational energy level and thus the tempera- ture. The consequence is a more uniform and faster heating of the materials than traditional ways of heat Correspondence to: S. Rimdusit (sarawut.r@chula.ac.th). Contract grant sponsor: Research Grant for Mid-Career University Faculty of the Commission on Higher Educa- tion, Ministry of Education, Thailand Research Fund 2005- 2007, Affair of Commission for Higher Education-CU Graduate Thesis Grant 2005-2006, TJTTP-JBIC Fund of Chulalongkorn University. Journal of Applied Polymer Science, Vol. 105, 1968–1977 (2007) V V C 2007 Wiley Periodicals, Inc.