Valorization of industrial by-products through bioplastic production: defatted rice bran and kraft lignin utilization

The objective of this study was to develop a bioplastic from industrial by-products. Commercial defatted rice bran (DRB) was extruded with 0-30% kraft lignin (KL) as a filler and 30% glycerol as a plasticizer. Firstly, the effect of extrusion temperature on the plasticized DRB's processability was determined. Increasing the die extrusion temperature from 100 degrees C to 150 degrees C improved the extrudability by decreasing the die pressure and motor current. Subsequently, the effect of KL on plasticized DRB was studied. The addition of 10-30% KL improved DRB processability. The addition of 30% KL markedly lowered the die pressure in comparison to using a 150 degrees C extrusion temperature. Moreover, KL addition decreased DRB viscosity determined by a capillary rheometer. These results were coherent with a decreased storage modulus in a rubber state and an increased tan d height determined by a dynamic mechanical thermal analyzer (DMA). However, n values of DRB with 10-30% KL could not be explained by a simple mixing rule. This may be attributed to the interaction between DRB and KL, as shown by Fourier transform infrared (FTIR) spectra. KL addition increased Young's modulus and the glass transition temperature (T-g) of plasticized DRB. Therefore, blending DRB with KL is an effective way to improve polymer flowability at the processing temperature and mechanical properties at ambient temperature.