Effect of the sorbitol to glycerol weight ratio and sugarcane bagasse concentration on the physicomechanical properties of wheat starch-based biocomposite

Abstract

Abstract This study involved fabricating thermoplastic wheat starch–sugarcane bagasse biocomposites through melt mixing method. The effect of sugarcane bagasse concentration at 3 levels of 0 wt.%, 7.5 wt.% and 15 wt.% of wheat starch and sorbitol:glycerol weight ratio at 4 levels of 0:4, 1:4, 2:4 and 4:4 on their physicomechanical properties was evaluated. The results indicated that increasing both of the weight ratio of sorbitol to glycerol and the concentration of bagasse generally led to a significant increase in tensile strength and modulus, but a decrease in elongation at break and equilibrium moisture content. The biocomposite containing the weight ratio of sorbitol:glycerol of 0:4 and bagasse concentration of zero, had the lowest tensile strength (0.22 MPa) and tensile modulus (0.23 MPa), and the highest elongation at break (103.1%) and equilibrium moisture content (30.6%) and conversely The biocomposite containing the weight ratio of sorbitol:glycerol of 4:4 and bagasse concentration of 15, had the highest tensile strength (5.3 MPa) and tensile modulus (371.5 MPa), and the lowest elongation at break (1.5%) and equilibrium moisture content (20.6%). Moisture absorption was also studied using the Peleg model, which showed that samples with lower weight ratios of sorbitol to glycerol and lower bagasse concentrations had higher initial moisture absorption rates and greater moisture absorption capacity. The investigation of thermal behavior of the biocomposites by TGA analysis showed improved thermal stability of the biocomposites by increasing both of the sorbitol:glycerol weight ratio and the bagasse concentration. Finally, the FTIR spectrum revealed an increase in hydrogen and polar bonds in the biocomposites compared to pure starch. Graphical Abstract

Keywords

• Biocomposite
• Natural fibers
• Plasticizer
• Thermoplastic starch