A biopolymer composite, thermoplastic cassava starch (TPCS) was reinforced with natural fibers and glycerol as a plasticizer. Paper fiber and vetiver fiber were used as a reinforcing material in this study. The mixture experimental design approach was applied in order to develop mathematical models that can be used to determine the formulation of TPCS biocomposites correlated to output properties. Statistical methods were used to obtain models used to estimate or predict the required properties of the biocomposites. The thermoplastic cassava starch reinforced by paper fiber was studied as a preliminary experiment, which provide the suggested proportions of the components to be used with the thermoplastic cassava starch based on vetiver fiber. The formulations of thermoplastic cassava starch reinforced by paper fiber were statistically analyzed by maximizing performance of the biocomposites. In this study, mechanical properties of thermoplastic composites were improved compared to pure TPCS (without natural fibers) at the weight fractions of 65 wt.% cassava starch and 35 wt.% glycerol. The tensile strength of pure TPCS was increased from 0.7 MPa to 11.6 MPa or increased by 16.5 times at a weight fraction of 66 wt.% cassava starch, 21 wt.% glycerol and 13 wt.% vetiver fiber, while the elongation was reduced from 65.8 % to 14.5 %. The elongation decreased when the cassava starch load increased, associated with the decrease of glycerol. SEM micrographs showed good adhesion between starch and fibers but dispersion was not uniform. The thermal stability of TPCS reinforced by natural fibers was improved compared to the unreinforced material.Biodegradation of thermoplastic cassava starch biocomposites was examined in a simulated aerobic composting environment using a direct measurement respirometric (DMR) system in accordance with the ASTM D5338 and ISO 14855 standards. The thermoplastic cassava starch reinforced by vetiver fiber was easily biodegraded and almost all samples reached above 70 % mineralization in MSU compost. Differences in biodegradation rates were attributed to the intrinsic properties of the compost such as moisture content, pH, and nutrients for the microbes. In addition, a mathematical model for biodegradability correlated to the component proportions of inputs was obtained. The ANOVA test showed that the model was sufficiently reliable to be useful in design of the composites.A preliminary life cycle assessment (LCA) was conducted according to the ISO 14040 series framework. Comparison of the environmental impacts for two formulations of 1 kg of pellets of thermoplastic cassava starch reinforced by vetiver fiber and a conventional biopolymer, granulated polylactide, showed that the environmental performance of the two formulations were not dramatically different. The major energy consumption was from the electricity for the laboratory scale manufacturing. When compared with the granulated polylactide, the abiotic depletion, eutrophication and global warming (GWP100) of the TPCSV resin were slightly lower than that of the granulated polylactide. Acidification and ozone layer depletion (ODP) were slightly higher than for the granulated polylactide. This study indicated there is no clear winner between two types of materials especially considering the variability of the data and their extraction from different biomass sources.
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