Enhanced properties of low-density polyethylene composites reinforced with Bridelia ferruginea fibers: effect of low temperature fiber acetylation

In this study, lignocellulosic fibres were extracted from Bridelia ferruginea (BF), a shrub which can be found in sub-Saharan Africa with a view to probing the potential application of the fibres. The chemical properties of the BF were chemically modified by acetylation to evaluate the potential applications of the fibre reinforced polymer composites. The unacetylated and acetylated fibres were characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA) to compare thermal and crystallographic properties after acetylation over different lengths of time. The acetylated fibres with the most promising properties were used for the fabrication of a polymeric composite. The mechanical properties of the fibre-reinforced polymer composites were studied by hardness and dynamic mechanical measurements. Four types of polymeric samples were prepared for the mechanical measurements: unreinforced polymer (Control) polyester, ATBF/LDPE, ACEBF3/LDPE, ACEBF/LDPE. The SEM micrographs revealed that acetylation led to defibrillation. FTIR peaks at 1250 cm−1 and 1371 cm−1 confirmed that acetylation had occurred. The fibres possessed high crystallinity index of 75% which reduced as time of acetylation increased. Acetylation at mild conditions of 70 °C for 3 h did not result in significant damage to the fibres. For the hardness measurements, the values of the micro-hardness of the composite samples increased from 0.20 GPa to 0.29 GPa. The acetylated fibres tend to further resist deformation due to its dispersion in the polymer matrix providing a stronger cross-linking effect. The properties unearthed show that BF appears to be a promising raw material for the production of polymer composites.