Morphological, thermal and mechanical properties of benzoxazine resin reinforced with alkali treated alfa fibers

Abstract This paper explores a new class of composites based on bisphenol-A aniline benzoxazine (BA-a) and alfa fibers for which the aim is to enhance the properties of BA-a resin and investigate the ability of natural fillers to mitigate some of its outcomes. For this purpose, natural Alfa fibers (NAF) are firstly treated by an alkaline solution to obtain treated alfa fibers (TAF) then incorporated into BA-a at different loadings from 5 to 30 wt.% to form composites. The effect of the alkali treatment on the NAF was investigated through Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscope (SEM). The results revealed a partial removal of hemicellulose and lignin with a better thermal stability and rougher surfaces. The influence of adding the TAF on the mechanical, morphological, thermal and thermomechanical features in addition to the curing behavior of the obtained composites was thoroughly investigated. The obtained results revealed significant improvements in micro-hardness, flexural and thermomechanical features compared to the unfilled resin. Moreover, the presence of numerous hydroxyl groups (OH) induced a strong fiber-matrix adhesion, a better stress-transfer with a consequence enhancement in the glass transition temperature.