Sayote (Sechium edule) fiber isolated at varying acid hydrolysis time and reinforcement to starch/PVOH composite blends

The chemo-mechanical extraction of sayote (Sechium edule) fibers and their use as reinforcement to biodegradable starch/polyvinyl alcohol composite blends were studied. Fourier transform infrared analysis revealed the removal of hemicelluloses from the fiber surface after 7 and 10 h of acid hydrolysis time. Scanning electron micrographs show the removal of surface impurities during chemical-mechanical treatment. There was a more exposed fiber surface after 7 and 10 h of acid hydrolysis time. However, fibers acid hydrolyzed for 10 h revealed the presence of more cracks on the fiber surface. X-ray diffraction analysis showed that 7 h acid hydrolyzed fiber had the highest relative crystallinity index of 64.9% as compared to the fiber that was acid hydrolyzed for 10 h with a relative crystallinity index of 58.6%. Both 7 h and 10 h acid hydrolyzed fibers gave 20% yield after extraction. The fiber that was hydrolyzed for 7 h was used as reinforcement to starch/polyvinyl alcohol composite and gave a bending and tensile strength of 5.36 MPa. The unreinforced composite gave a bending and tensile strength of 2.85 MPa. The scanning electron micrograph of the reinforced composite revealed a more homogeneous surface and lesser starch granule exposure as compared to the unreinforced composite with a rough and bumpy surface. The onset of degradation and carbonization of the fiber reinforced composite was seen at around 280 and 580 °C respectively.