Preparation and characterization of highly filled graphite-based polybenzoxazine composites

Abstract

This research aims to study suitable preparation methods and to characterize highly filled graphite composites using polybenzoxazine as a matrix. The high loading of graphite filler was attained in the range of 40 to 80% by wt. due to the very low a-stage viscosity of the benzoxazine resin (BA-a) used. The suitable condition for the compression molding of the highly filled graphite-polybenzoxazine (PBA-a) composites was at temperature of 200°C, and pressure of 15 MPa in the hydraulic hot-press machine for 3 hours to assure a fully cured specimen. The densities of the obtained composites were found to be in a range of 1.19-1.88 g/cm³. Mechanical and thermal properties of these composites were studied by dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). The experimental results revealed that at the maximum content of 80wt% or 68vol% of graphite filled in the polybenzoxazine, storage modulus at room temperature of the specimen was raised from 5.9 GPa of the neat polybenzoxazine to about 21.9 GPa in the composites. Finally, glass-transition temperatures (Tg) of the prepared composites were observed to be ranging from 174 to 194°C. The Tg values substantially increased with increasing the graphite contents implying substantial interfacial interaction between the filler and the matrix.