| Abstract |
This thesis focuses on the research, development, and study of nanocomposite and composite materials with controllably modified characteristics (mechanical, electrical, and physical properties), such as tensile strength, flexural strength, Modulus of elasticity, dielectric constant, and conductivity. Advanced nanocomposite filaments were fabricated in this research following a melt mixing process to improve the mechanical and electrical functional properties of three-dimensional (3D) printed structures developed using commercially available Fused Filament Fabrication (FFF) 3D printers. Moreover, an extensive study has been made regarding the effect of multiple successive thermomechanical processes on the pure polymer matrices’ mechanical and physical properties, used in this study, to provide an insight of their sustainability and performance in material extrusion (MEX) 3D printing, in which the FFF process belongs.
For this research, novel nanocomposite filaments made of Acrylonitrile butadiene styrene (ABS), High-density polyethylene (HDPE), and Low-density polyethylene (LDPE) matrices were developed in this study with incorporation of various filler concentrations of Graphene nanoplatelets, Titanium Dioxide, Zinc Oxide, Antimony Tin Oxide, and Magnetite for applications in fused filament fabrication (FFF), an approach not previously presented in the literature regarding the nanofillers used with these specific polymer matrices and the methodology applied in the current study, by using melt extrusion and 3D-Printing. The use of nanofillers can not only change but also considerably increase the mechanical response of a polymer matrix, according to the overall assessment of the results. This work aided in developing novel composite polymeric materials not only for 3D printing but for exploitation also in large-scale industrial extrusion use by offering in some cases more than a 50 % increase in tensile, impact, and or flexural strength when compared to unfilled polymer matrix parts.
This thesis exploits the particular positive characteristics of the nanofillers, such as the large surface area interactions and their increased mechanical and electrical properties, to develop composites with various commercially available polymeric matrices to induce higher mechanical and electrical properties that the industry can benefit from.
Finally, multiple characterization techniques were carried out to identify and analyze the structural condition of the produced specimens and the filament material, the effect on the thermal properties of the polymers used and the thermal properties of the composite and nanocomposite materials produced, and characterization techniques to get a glimpse of the fillers’ dispersion on each polymer matrix used along with the layer fusion in each case.
Finally, in addition to the above research, it was found that heating processes can increase the mechanical properties of pure polymer matrices and even increase their mechanical strength for a certain number of heating repetitions i.e., melt extrusion and 3D printing. The best overall mechanical behavior was found between the third and the fifth heating repetition (reprocessing step), indicating a significant positive impact of the polymers’ reprocessing, besides the environmental one of possible reprocessing and recycling these types of polymers to reduce pollution waste. This part of the research was done to identify any effect the extrusion and 3D printing processes may have on the mechanical properties of the unfilled polymer before adding fillers.
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