Flax fiber-reinforced plastic composites have attracted increasing interest because of the advantages of flax fibers, such as low density, relatively high toughness, high strength and stiffness, and biodegradability. Thus, oilseed flax fiber derived from flax straw, a renewable resource available in Western Canada, is recognized as a potential replacement for glass fiber in composites. Among plastics, polyethylene is a suitable material for use as a matrix in composites. However, there are not many studies in this area. Therefore, the main goal of this research was to develop flax fiber-polyethylene (PE) biocomposites via injection molding and investigate the effect of material properties and processing parameters on their properties. <p>Alkali, silane, potassium permanganate, sodium chlorite, and acrylic acid treatments were employed to flax fiber to decrease the hydrophilic of fiber and improve the adhesion between the fiber and the matrix. All chemically treated fiber-HDPE biocomposites had higher tensile strength and lower water absorption compared with non-chemically treated ones. Acrylic acid treatment of the fiber resulted in slight increase in its degradation temperature; using this treated fiber resulted in biocomposites with the best performance. Therefore, the morphological, chemical, and thermal properties of acrylic acid treated fiber were also studied. <p>Linear Low Density Polyethylene (LLDPE) and High Density Polyethylene (HDPE) were the main matrices investigated in this research. Showing a high tensile strength and similar water absorption, HDPE was used as the matrix in further research. Flax fiber with 98-99% purity was chosen as reinforcement since the flax shive mixed with the fiber decreased the tensile and flexural properties but increased the water absorption of the biocomposite. <p>Acrylic acid-treated fiber-HDPE biocomposites had been developed through injection molding under different processing conditions. Increasing the fiber content of biocomposite increased its tensile and flexural strengths, especially flexural modulus, but its water absorption capacity also increased. It was possible to improve the mechanical properties of biocomposites and decrease the water absorption by adjusting injection temperature and pressure. Injection temperature had more influence on the quality of the biocomposite than injection pressure. Injection temperature lower than 195°C was recommended to achieve good composite quality. <p>Melts of HDPE and flax fiber-HDPE biocomposites were categorized as power-law fluids. Apparent viscosity, consistency coefficient, and flow behavior index of biocomposites were determined to study their flow behavior. The statistical relationship of these parameters with temperature and fiber content were modeled using the SAS and SPSS softwares. The injection filling time was related to the material rheological properties: biocomposites required longer filling time than pure HDPE. Low injection temperature also resulted in long filling time.<p>The thermal conductivity, thermal diffusivity, and specific heat of biocomposites containing 10, 20, and 30% fiber by mass were determined in the processing temperature range of 170 to 200°C. Fiber content showed a significant influence on the thermal properties of the biocomposites. The predicted minimum cooling time increased with the thickness of the molded material, mold temperature, and injection temperature, but it decreased with the ejection temperature.

This thesis explores the analysis and fabrication of plastic hypodermic needles. The hypotheses for this work are that replacing metal hypodermic needles with plastic ones will reduce or eliminate the possibility of the second-hand infections from needle sticks and unsterlized reuse and will be more cost and time efficient to recycle. The most critical structural failure mode for plastic needles is buckling due to their shape (thin walled hollow column). The consideration of buckling is critical to avoid structural failure and to ensure reliability for medical applications. The buckling strength of a cannula is analyzed by analytic (Euler buckling theory) and finite element analysis (FEA) methods. A 22 gage needle model (OD 0.7mm, ID 0.4mm, Length 12.7mm) was analyzed. Euler buckling theory was used to calculate the critical buckling load. Numerical approaches using finite element analyses showed very similar results with analytic results. A skin model was introduced to simulate boundary conditions in the numerical approaches. To verify the results of the analyses, cannulas with the same cross-sectional dimensions were fabricated using a micro injection molding technique. To make the parts hollow, a core assembly of straightened wire was used. Using the tip of a 22 gage needle, cannulas with the inverse shape of an actual hypodermic needle were made. The structural (buckling) characteristics of cannulas were measured by a force-displacement testing machine. When buckling occurred, an arch shape was visible and there was an abrupt change in the load plot. Test results showed the relation between the needles length and the buckling load, which was similar to that predicted by Euler buckling theory. However, test values were 60% of the theoretical or analytical results. Several reasons to explain these discrepancies can be found. The first is that an unexpected bending moment resulted from an eccentric loading due to installation off-center to the center of the testing machine or to the oblique insertion. A cannula that was initially bent during ejection from the mold can add an unexpected bending moment. The quality control of cannulas can be another reason. Bent or misaligned core wires produce eccentric cannulas, and the thinner wall section can buckle or initiate fracture more easily. The last reason may be that Euler buckling theory is not fully valid in short cannula, because the axial stress reaches yield stress before buckling occurs. Inelastic deformation occurs (i.e., the modulus is reduced) during compression in short cannula. The Johnson column formula is introduced to explain this situation. Especially for the nylon nanocomposite material tested, a loss in modulus due to moisture absorption may be another explanation for the discrepancies.

Replacing steel and wood with plastic is the developing trend in the modern industry. In many shaping processing methods¡M the injection molding technology is widely used in plastic industry for its good adaptability¡M high producing efficiency and easy-achieve to automation. Injection molding is a very complicated physical process¡M the molding parameters (including temperature¡M pressure¡M time¡M speed and position etc) and environment condition will directly affect the flowing condition of melting plastic and final quality of products¡M so to obtain the best molding parameters is the key to improve the quality of the plastic products. The traditional method of adjusting parameters is try and error¡M which wastes time and materials. And it¡¦s also hard to accumulate and transmit experience¡M so we urgently need to find a new method. By going through a long time of experiment and exploring¡M we found that the DOE (Design of Experiment)¡M which is one of the most important tools of 6 sigma¡M can be applied to improving the molding processing¡M and it will bring us the innovation of injection molding technology. DOE is one of the mathematic methods¡Mwhich bases on Probability theory¡M Statistics and Linear algebra¡M through rationally arrange experiment and correctly analyze the results of experiment¡M to obtain the best parameters. In the processing of exploring¡M we have obtained first-step success in shortening cycles¡M reducing weight of product and improving qualities. For the sake of extending and developing the methods of DOE applied to molding technology in the company and transmitting experience of experts¡M we are going to conclude many DOE cases as a rule¡M establish a database¡M develop an injection molding expert system¡M which will be the effective way to bring cost down¡M improve efficiency and establish a core-competition capability of injection molding technology.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 116).

Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 1999. / Word processed copy. Summary in English. Includes bibliographical references (leaves 95-99). Also available online.

published_or_final_version / abstract / toc / Mechanical Engineering / Master / Master of Philosophy

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