Characterisation of natural cellulosic fibre from Pennisetum purpureum stem as potential reinforcement of polymer composites

Highlights: • The treated fibres had an average diameter of less than 0.21 ± 0.03 mm. • Moisture content of treated fibres reduced with increased alkaline concentration. • Morphological study shows that the treated fibre's surface became rougher. • The 5% alkali-treated fibre yields average maximum tensile stress of 141 ± 24 MPa. Pennisetum purpureum (PP) fibres were comprehensively characterised to assess their potential as reinforcing materials in polymer composites. The fibres were treated with 5, 7, 10, 12, and 15% sodium hydroxide wt.% concentration for 24 h. The fibres were subjected to single fibre tensile tests, thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The average diameter of the untreated fibres was 0.24 ± 0.02 mm, and the treated fibres had an average diameter of less than 0.21 ± 0.03 mm, yielding a 12–45% reduction in the diameter. The moisture content of the treated fibres decreased as the concentration of the alkali increased. The morphological observation demonstrated that as the alkali concentration increased, the fibre becomes more compressed due to collapse the cellular/lumen structure, the void content decreased, and its surface became rougher. The 5% alkali-treated fibre achieved an average maximum ultimate tensile stress of 141 ± 24 MPa. Young's modulus on the other hand, decreased from an average of 5.68 ± 0.14 GPa for untreated fibre to only 0.55 ± 0.17 GPa as the alkali concentrations increased from 5 to 15%.