Pre-treatment of flax fibers for use in rotationally molded biocomposites
Flax fibers can be used as environmentally friendly alternatives to conventional reinforcing fibers (e.g., glass) in composites. The interest in natural fiber-reinforced polymer composites is growing rapidly due to its high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost and low density. These advantages place natural fiber composites among the high performance composites having economic and environmental advantages. In the field of technical utilization of plant fibers, flax fiber-reinforced composites represent one of the most important areas. On the other hand, lack of good interfacial adhesion and poor resistance to moisture absorption make the use of natural fiber-reinforced composites less attractive. In order to improve their interfacial properties, fibers were subjected to chemical treatments, namely, mercerization, silane treatment, benzoylation, and peroxide treatment. Selective removal of non-cellulosic compounds constitutes the main objective of the chemical treatments of flax fibers to improve the performance of fiber-reinforced composites. The objective of this study was to determine the effects of pre-treated flax fibers on the performance of the fiber-reinforced composites. Short flax fibers were derived from Saskatchewan-grown flax straws, for use in fiber-reinforced composites. Composites consisting of high-density polyethylene (HDPE) or linear low-density polyethylene (LLDPE) or HDPE/LLDPE mix, chemically treated fibers and additives were prepared by the extrusion process. Extrusion is expected to improve the interfacial adhesion significantly as opposed to simple mixing of the two components. The extruded strands were then pelletized and ground. The test samples were prepared by rotational molding. The fiber surface topology and the tensile fracture surfaces of the composites were characterized by scanning electron microscopy to determine whether the modified fiber-matrix interface had improved interfacial bonding. Mechanical and physical properties of the composites were evaluated. The differential scanning calorimetry technique was also used to measure the melting point of flax fiber and composite. Overall, the scanning electron microscopy photographs of fiber surface characteristics and fracture surfaces of composites clearly indicated the extent of fiber-matrix interface adhesion. Chemically treated fiber-reinforced composites showed better fiber-matrix interaction as observed from the good dispersion of fibers in the matrix system. Compared to untreated fiber-reinforced composites, all the treated fiber-reinforced composites had the same tendency to slightly increase the tensile strength at yield of composites. Silane, benzoylation, and peroxide treated fiber-reinforced composites offered superior physical and mechanical properties. Strong intermolecular fiber-matrix bonding decreased the high rate of water absorption in biocomposites. The incorporation of 10% untreated or chemically treated flax fibers also increased the melting point of composites. Further investigation is required to address the effect of increase in fiber content on the performance of composites.
DegreeMaster of Science (M.Sc.)
DepartmentAgricultural and Bioresource Engineering
ProgramAgricultural and Bioresource Engineering
SupervisorTabil, Lope G.
CommitteePanigrahi, Satyanarayan; Maule, Charles P.; Zhang, W. J. (Chris)
Copyright DateJuly 2004