Valorization of agricultural waste to polybenzoxazine-carbon composites: Studies on microstructure, thermal and dielectric properties

Abstract

Agricultural waste valorization has become a necessity to reduce global warming. In this context, absolute bio-waste derived cardanol, furfurylamine (ffa), and benzaldehyde were utilized for the synthesis of a novel card-bisphenol (BBC) and its benzoxazine (BBC-ffa) resin. Further, the reinforcement of carbon building blocks derived from three different sustainable resources, viz. Anacardium occidentale, Borassus flabellifer, and Tamarindus indica and named cashew apple carbon (CC), palmyra palm inflorescence (spadix) carbon (PC), and tamarind seed carbon (TC), respectively. The derived carbons were reinforced (1–20 wt%) separately with BBC-ffa polymer matrix [poly(BBC-ffa)] for the engineering of carbon integrated polybenzoxazine composites [poly(BBC-ffa)–CC/PC/TC] to achieve high-k dielectrics. Because the carbon with different functionalities intrinsically exhibit higher polarization and lower specific surface area. Dielectric constant (k) of the polybenzoxazine matrix (k = 4.62) has been increased to 8.58, 9.43, 10.60 for the reinforcement of 20 wt% of each CC, PC, and TC polybenzoxazine composites, respectively and the value of dielectric loss was also significantly decreased for the same. The dissemination of reinforced carbon particles in the polybenzoxazine matrix was ascertained through the surface analysis of the composites by FE-SEM. Based on the results of TGA, the carbon reinforced composites showed slightly lower thermal stability and about two-fold higher char yield than that of neat polybenzoxazine. Hydrophobicity of the composites enhanced with increasing the carbon content. The resulting sustainable polybenzoxazine-carbon composites could be effectively utilized as a gate dielectric in microelectronics.