Enhancing mechanical properties, degradation rate, and water resistance of bioplastic Lignin/Polyvinyl Alcohol (PVA) by fractionation of lignin

The growing need for biodegradable polymers has resulted in heightened scientific investigation into developing biodegradable polymers with comparable properties to conventional polymers. One of the new materials that can be utilized to improve the performance of bioplastic is lignin. In order to obtain lignin with homogeneous properties, one of the viable options is the use of fractionation process. In this research, polyvinyl alcohol (PVA) was blended with fractionated lignin and non-fractionated lignin to improve mechanical properties, biodegradation, and water resistance of bioplastic PVA. Fractionated lignin is evaluated by gel permeation chromatography (GPC), which verifies the decrease in molecular weight of the lignin. Observation of lignin/PVA blends using scanning electron microscopy (SEM) showed the fractionation of lignin resulted in a more homogeneous blend of lignin/PVA. Fourier transform infrared spectroscopy (FTIR) confirms that the blending process of lignin and PVA is mainly physical interaction. Adding fractionated lignin up to 50%wt increased the maximum tensile strength of 20.31 MPa and elastic modulus of 1.31 GPa. However, the elongation at break is reduced to 16.35% compared to the non-fractionated lignin counterpart. Meanwhile, adding fractionated lignin up to 30%wt to PVA increased the tear strength of the blend with the maximum tear strength of 58.30 N/mm. The degradation rate of lignin/PVA blend using fractionated lignin is noticeably higher compared to lignin/PVA blend using non-fractionated lignin. Moreover, the addition of lignin to PVA increased the water resistance of lignin/PVA bioplastic. In summary, the findings of this work demonstrate that the fractionation of lignin is a viable approach for enhancing the properties of PVA bioplastic.