Mechanical properties of thermoplastic starch / oil palm empty fruit bunch biocomposite film

Abstract

This paper discusses the effect of oil palm empty fruit bunch (OPEFB) filler loading on the mechanical properties of thermoplastic starch/oil palm empty fruit bunch (TPS/OPEFB) biocomposite film. OPEFB filler was extracted from raw OPEFB by cleaning, grinding, ring milling and sieving processes to obtain 150μm lignocellulosic fibers. The fibers were then subjected to alkaline and acid treatment to obtain the cellulose (filler). TPS matrix was prepared by combiSning the distilled water, corn starch and glycerol under thermomechanical process (stirring and heating). OPEFB filler in 1wt%, 2wt%, 3wt%, 4wt%, and 5wt% was added into the TPS matrix. The TPS/OPEFB mixture was casted in teflon pan and dried in oven (45 °C) for 24 hours to form the biocomposite film. Results indicated that the TPS/OPEFB biocomposite films have better tensile strength and Young's modulus compared to the pure TPS film. Tensile strength of the biocomposite showed an increasing trend when the OPEFB filler loading was increased from 1wt% to 4wt%. Significant increment of tensile strength could be observed when 4wt% OPEFB filler was added into the TPS matrix. The TPS/OPEFB biocomposite with 4wt% OPEFB achieved the highest tensile strength value (4.51 MPa), which was 109.8% higher than the pure TPS. However, further increase of OPEFB loading to 5wt% resulted in the decrease of the tensile strength of the biocomposite. Young's modulus of the biocomposite followed the trend of the tensile strength, where the addition of OPEFB from 1wt% to 4wt% resulted in the continuous improvement of the Young's modulus value. Interestingly, the addition of 4wt% OPEFB led to tremendous increment of Young's modulus. When benchmarked with the pure TPS, the Young's modulus of the TPS/OPEFB biocomposite with 4wt% OPEFB loading increased by 364%. Further addition of OPEFB to 5wt% decreased the Young's modulus of the biocomposite to 1.10 MPa. This could be due to the overcrowding of the OPEFB cellulose in the TPS matrix, poor dispersion of filler, reduction in the filler-matrix interactions that inhibit efficient stress transferring mechanism from matrix to filler.