A feasibility study on using surface treated kaolin mineral in thermoplastic composites

Abstract

Glass fiber reinforced plastics are the current state of the art, mainly in automotive manufacturing applications. With the industry’s trend towards weight reduction for fuel economy and enhanced performance, an improvement in material composition is needed. This thesis investigates the possibility of using surface-treated kaolin mineral fillers as a substitute or a complement to glass fibers in nylon composites. An experimental approach is utilized to determine their properties and compare them to existing materials in the industry. Specimens are fabricated using a twin-screw tabletop micro-extruder for the first phase of the study, and a 75-ton injection molding machine, which compares to the industrial standard, for the second phase. Mechanical tests, thermal tests, and density measurements are used to evaluate the composite material properties. SEM imaging is used to investigate filler morphology and its distribution within the matrix, as well as voids and defects. A comparison between lab-scale and scale-up fabrication techniques is used to highlight the effects of manufacturing conditions. A micromechanical model is employed to compare experimental results to theoretical predictions. Results suggest that high aspect ratio fillers increase the strength and stiffness of the composite. Conversely, low aspect ratio particles improve impact strength. Furthermore, particle size affects the dispersion of the mineral, with minerals predicted to have a smaller particle size showing less agglomeration. Blending multiple mineral morphologies showed a synergistic effect in resulting properties. Similar trends were found in both phases of the study indicating that lab scale fabrication can be used as a screening to investigate the reinforcing ability of the minerals.