A thesis submitted in partial fulfillment of the requirement for the Degree of Master Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 2010

In this study, the alkali treatment was used to extract fiber bundles from corn husk. Biocomposites from soy protein and polylactic acid reinforced with corn husk fiber before and after alkali was prepared and the properties of performance were investigated. SEM obsevations on the morphological structure of untreated corn husk fiber showed the thick outer layer of non-cellulosic substances on the surface of fiber. The mechanical properties of PLA {u2013}soy based biocomposites reinforced with corn husk fiber after extraction was superior to the untreated fiber. Optimum condition for extracted corn husk fiber was 1% w/w of NaOH solution at 70°C for 2h of reaction because this condition showed the maximum increased the value of all mechanical properties. The maximum value of tensile, flexural and impact strength are 13.67 MPa, 27.23 MPa and 1.59 kJ/m2, respectively after improvement. The effect of PLA {u2013}Soy protein based biocomposites reinforced with corn husk fiber before and after fiber surface modification was prepared for investigation the mechanical and water absorption properties. Silane treatment and potassium permanganate treatment were used for fiber surface modifications. These agents were improved the mechanical and reduce the hydrophilicity of natural fiber. SEM obsevations on the morphological structure of corn husk fiber showed that chemical agents can be removed impurities substances such as hemicellulose and lignin after surface modification. The experimental result showed that fiber after surface modification was significantly improving the mechanical and water absorption properties because the agents made a strong interfacial between fiber and matrix. Similarity, SEM observations on the tensile fracture surface of biocomposites showed that the surface modification of the fiber occurred and improved fiber{u2013}matrix adhesion. Regarding the mechanical properties of biocomposites, it was observed that the PLA-Soy protein based biocomposites with 1.5% silane solution treated corn husk fiber showed maximum improvement when compared with the other treatments. Furthermore, the optimum in mechanical properties can be obtained at fiber content of 5wt%which exhibit an obvious enhancement in strength and modulus compared to the other fiber contents. Approximately 53% improvement in tensile strength, 124% in tensile modulus, 86% in flexural strength, 126% in flexural modulus, 37% in impact strength and 11% in water absorption had been found, respectively when compared with untreated corn husk fibers. Additional, water sorption kinetics in 1.5% silane treated corn husk fiber reinforced PLA-Soy protein based biocomposites was investigated. Water sorption at four different temperatures was analysed and compared. The saturation of soaking time was shortened when the temperature of immersion was increased because of higher rate of diffusion. Higher diffusion coefficients, sorption coefficient and permeability coefficient values were observed at 70°C whereas lower diffusion coefficients, sorption coefficient and permeability coefficient values were observed at 4°C.