Thermal and mechanical analyses of biocomposites from cardanol-based polybenzoxazine and bamboo fibers

Abstract

The aim of this work was to evaluate the thermal and mechanical properties of new biocomposites, using bamboo fibers as reinforcements in a cardanol-based polybenzoxazine matrix, using diethylenetriamine (DETA) as catalyst. The natural bamboo fibers underwent an alkaline treatment for a better compatibility with the polymer matrix and increase the crystallinity degree. The untreated and treated fibers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction, while the bio-based benzoxazine was characterized by nuclear magnetic resonance (1H-NMR) spectroscopy and FT-IR. The thermal polymerization behavior of the benzoxazine with and without the presence of DETA was analyzed by differential scanning calorimetry, and it was observed that with the presence of the catalyst (5%), the initial temperature of polymerization (Te) was reduced by 47 °C. The polymer and the biocomposites were also analyzed by FT-IR, observing the main polymer structure and confirming the presence of the bamboo fibers. The obtained biocomposites were characterized by dynamic mechanical analysis and thermogravimetric analysis (TG). It was noticed the addition of the bamboo fibers increased the storage modulus (E′) and glass transition temperature of the material, but the thermal stability was affected negatively with the addition of reinforcements.