Master of Science / Department of Mechanical and Nuclear Engineering / Gurpreet Singh / 3D-printing is a popular manufacturing technique for making complex parts or small quantity batches. Currently, the applications of 3D-printing are limited by the material properties of the printed material. The processing parameters of commonly available 3D printing processes constrain the materials used to a small set of primarily plastic materials, which have relatively low strength and electrical conductivity. Adding filler materials has the potential to improve these properties and expand the applications of 3D printed material. Carbon nanomaterials show promise as filler materials due to their extremely high conductivity, strength, and surface area. In this work, Graphite, Carbon Nanotubes, and Carbon Black (CB) were mixed with raw Acrylonitrile Butadiene Styrene (ABS) pellets. The resulting mixture was extruded to form a composite filament. Tensile test specimens and electrical conductivity specimens were manufactured by Fused Deposition Method (FDM) 3D-printing using this composite filament as the feedstock material. Weight percentages of filler materials were varied from 0-20 wt% to see the effect of increasing filler loading on the composite materials. Additional tensile test specimens were fabricated and post-processed with heat and microwave irradiation in attempt to improve adhesion between layers of the 3D-printed materials. Electrical Impedance Spectroscopy tests on 15 wt% Multiwalled Carbon Nanotube (MWCNT) composite specimens showed an increase in DC electrical conductivity of over 6 orders of magnitude compared to neat ABS samples. This 15 wt% specimen had DC electrical conductivity of 8.74x10−6 S/cm, indicating semi-conducting behavior. MWCNT specimens with under 5 wt% filler loading and Graphite specimens with under 1 wt% filler loading showed strong insulating behavior similar to neat ABS. Tensile tests showed increases in tensile strength at 5 wt% CB and 0.5 wt% MWCNT. Placing the specimens in the oven at 135 °C for an hour caused increased the stiffness of the composite specimens.

Biodiesel and hydrotreated vegetable oil (HVO) are currently viewed by the transportation sector as the most viable alternative fuels to replace petroleum-based fuels. The use of biodiesel has, however, been limited by the deteriorative effect of biodiesel on rubber parts in automobile fuel systems. This work therefore aimed at investigating the degradation of acrylonitrile butadiene rubber (NBR) and fluoroelastomers (FKM) on exposure to biodiesel and HVO at different temperatures and oxygen concentrations in an automated ageing equipment and a high-pressure autoclave. The oxidation of biodiesel at 80 °C was promoted by an increase in the oxygen partial pressure, resulting in the formation of larger amounts of hydroperoxides and acids in the fuel. The fatty acid methyl esters of the biodiesel oxidized less at 150 °C on autoclave aging, because the termination reactions between alkyl and alkylperoxyl radicals dominated over the initiation reactions. HVO consists of saturated hydrocarbons, and remained intact during the exposure. The NBR absorbed a large amount of biodiesel due to fuel-driven internal cavitation in the rubber, and the uptake increased with increasing oxygen partial pressure due to the increase in concentration of oxidation products of the biodiesel. The absence of a tan δ peak (dynamical mechanical measurements) of the bound rubber and the appearance of carbon black particles devoid of rubber suggested that the cavitation was caused by the detachment of bound rubber from particle surfaces. A significant decrease in the strain-at-break and in the Payne-effect amplitude of NBR exposed to biodiesel was explained as being due to the damage caused by biodiesel to the rubber-carbon-black network. During the high-temperature autoclave ageing, the NBR swelled less in biodiesel, and showed a small decrease in the strain-at-break due to the cleavage of rubber chains. The degradation of NBR in the absence of carbon black was due only to biodiesel-promoted oxidative crosslinking. The zinc cations released by the dissolution of zinc oxide particles in biodiesel promoted reduction reactions in the acrylonitrile part of the NBR. Heat-treated star-shaped ZnO particles dissolved more slowly in biodiesel than the commercial ZnO nanoparticles due to the elimination of inter-particle porosity by heat treatment. The fuel sorption was hindered in HVO-exposed NBR by the steric constraints of the bulky HVO molecules. The extensibility of NBR decreased only slightly after exposure to HVO, due to the migration of plasticizer from the rubber. The bisphenol-cured FKM co- and terpolymer swelled more than the peroxide-cured GFLT-type FKM in biodiesel due to the chain cleavage caused by the attack of biodiesel on the double bonds formed during the bisphenol curing. The FKM rubbers absorbed biodiesel faster, and to a greater extent, with increasing oxygen concentration. It is suggested that the extensive biodiesel uptake and the decrease in the strain-at-break and Young’s modulus of the FKM terpolymer was due to dehydrofluorination of the rubber by the coordination complexes of biodiesel and magnesium oxide and calcium hydroxide particles. An increase in the CH2-concentration of the extracted FKM rubbers suggested that biodiesel was grafted onto the FKM at the unsaturated sites resulting from dehydrofluorination. / <p>QC 20170227</p>

The present study employs a standardized progressive load scratch test (ASTM D7027/ISO 19252) to investigate the fundamental physical and mechanistic origins of scratch deformation in styrene-acrylonitrile (SAN) random copolymers. Previous findings from numerical simulation using finite element methods are used to establish correlation between mechanical properties and key scratch deformation mechanisms of the SAN model systems. For SAN, the acrylonitrile (AN) content and molecular weight (MW) can be changed to alter mechanical properties such as tensile strength and ductility. The key scratch deformation mechanisms are identified as: scratch groove formation, scratch visibility, periodic micro-cracking and plowing. Groove formation has been correlated to the secant modulus at the compressive yield point while micro-cracking and plowing are related to the tensile strength of the material. The fundamentals and physical origins of scratch visibility are discussed. It is explained how unbiased evaluation is accomplished by means of an automatic digital image analysis software package (ASV®). Frictional behavior and the effects of scratch speed and moisture absorption are also addressed. Increasing the AN content and/or the MW of the SAN random copolymers generally enhances the scratch resistance of the material with regard to the onset of the key deformation mechanisms. Increasing the scratch speed increases the brittleness of the material, resulting in failure at lower applied loads. Moisture absorption increases with AN content and imparts a degree of plasticization as the moisture diffuses into the sub-surface. This plasticization initially results in a degradation of scratch resistance with respect to the key deformation mechanisms, but then, after saturation, the moisture on the surface provides lubrication and improves the scratch resistance. It is important to note that polymers are fundamentally different in nature, but the findings of this study serve as an important stepping stone down the path to a deeper understanding of polymer scratch behavior.

Acrylonitrile based engineering random copolymers were prepared via one step emulsion polymerization using ammonium persulfate (initiator), 1-dodecanthiol (chain transfer agent) and DOWFAX 8390 (surfactant) in the presence of water at approximately 65 0C. Three copolymer compositions were studied for novel polyacrylonitrile, (PAN)-polyhydroxyethyl acrylate (PHEA), PAN-polybutyl acrylate (PBA), novel PAN-polyt-butyl acrylate (PtBA), PAN-polyethyl acrylate (PEA) and PAN-polymethyl acrylate (PMA) with acrylate content varying from 8, 12 and 16 molar percent. Infrared spectroscopy, proton and carbon NMR were successfully utilized to confirm the chemical structure of copolymers. In order to determine the comonomer compositions in the copolymer structure, proton nuclear magnetic resonance, 1H NMR studies were carried out. Thermal (TGA, DSC) and mechanical properties of homo and copolymers were also investigated. Intrinsic viscosity (IV) measurements in dimethyl formamide (DMF) solution revealed that the molecular weight of the copolymers were quite enough to form ductile films. In this study, hydrogels and their copolymers of acrylonitrile (PAN-PHEA) were also studied. Some properties of the free standing copolymer films such as / swelling behaviors and densities were evaluated. It was also demonstrated that the nanocomposites of these copolymers could be utilized in filtration technology. Hence, novel PAN(88)-co-PMA(12) and polyaniline (PANI) nanocomposites were prepared at various PANI loadings to remove toxic chromium(VI) solution from water. Chemical structure, swelling and fracture morphology of the nanocomposites membranes were studied. It was observed that PANI had a great impact on the chromium removal. Permeate flux and rejection of chromium(VI) were demonstrated for various pHs and chromium(VI) concentrations. Finally, influences of comonomer composition on the thermal properties of the copolymers were investigated to input their structure property relation.

Acrylonitrile were copolymerized with 2-ethylhexyl acrylate and hexyl acrylate via one step emulsion polymerization using ammonium persulfate (initiator), 1-dodecanthiol (chain transfer agent) and DOWFAX 8390 (surfactant) in the presence of water at about 68 0C. Poly (acrylonitrile-2ethylhexyl acrylate) and poly (acrylonitrile-hexyl acrylate) copolymers with three different comonomer composition (8, 12 and 16 molar percent) were prepared. FTIR and 1H-NMR were used in order to clarify the chemical structure of copolymers. The comonomer amount incorporated into copolymers was determined by using 1H-NMR spectra. The thermal behavior of copolymers was determined by DSC and TGA. Molecular weights of copolymers were determined by intrinsic viscosity (IV) measurements. IV measurements revealed that both poly (acrylonitrile-2ethylhexyl acrylate) and poly (acrylonitrile-hexyl acrylate) have sufficient molecular weight to form nanoporous filtration membranes. Nanoporous filtration membranes were prepared and tested for chromium (IV) removal. It was observed that chromium (VI) rejections of nanoporous filtration membrane were highly dependent on the concentration and the pH of the solutions. Almost complete removal (99, 9 percent Cr (VI)) rejection was achieved at pHs 2, 5 and 7 for solution containing 50 ppm, chromium (VI) with permeate flux within a range from 177 to 150 L/m2h at 689.5 kPa. Also, chemical structure, swelling ratios, sheet resistivity and fracture morphologies of the nanoporous filtration membrane were studied. It should be noted that the nanoporous filtration membranes were fouling resistant.

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Indiana University-Purdue University Indianapolis (IUPUI) / Acrylonitrile Butadiene Styrene (ABS) is the most widely used thermoplastics in 3D printing for making models, prototypes, patterns, tools and end-use parts. However, there is a lack of systematic understanding of the mechanical properties of 3D printed ABS components, including orientation-dependent tensile strength, creep, and fatigue properties. These mechanical properties are critically needed for design and application of 3D printed components. The main objective of this research is to systematically characterize key mechanical properties of 3D printed ABS components, including tensile, creep, and fatigue properties. Additionally, the eff ects of printing orientation on the mechanical prop- erties are investigated. There are two research approaches employed in the thesis: rst, experimental investigation of the tensile, creep, and fatigue properties of the 3D printed ABS components; second, laminate based finite-element modeling of tensile test to understand the stress distributions in different printing layers. The major conclusions of the thesis work are summarized as follows. The tensile test experiments show that the 0 printing orientation has the highest Young's modulus, 1.81 GPa, and ultimate strength, 224 MPa. The tensile test simulation shows a similar Young's modulus as the experiment in elastic region, indicating the robustness of laminate based finite element model. In the creep test, the 90 printing orientation has the lowest k value of 0.2 in the plastics creep model, suggesting the 90 is the most creep resistant among 0 , 45 , and 90 printing orientations. In the fatigue test, the average cycle number under load of 30 N is 3796 revolutions. The average cycle number decreases to 128 revolutions when the load is below 60N. Using the Paris Law, with the crack size of 0.75 mm long and stress intensity factor is varied from 352 to 700 MN -m^3/2 , the predicted fatigue crack growth rate is 0.0341 mm/cycle.

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Additively manufactured fuels are becoming more common in the area of hybrid rockets due to the enhanced possibilities provided by computer aided design and improved additive material technology. When integrated with a highly compliant yet energetic paraffin wax, the additive manufactured material can help support the paraffin wax during the burn, and improve overall performance. This study investigates thin-walled acrylonitrile butadiene styrene structures that separate paraffin wax into azimuthally partitioned cells. The fuel grains are tested using a vertical test stand, custom nitrous system, and data acquisition system. The computer program Chemical Equilibrium with Applications is used to compare common hybrid fuels such as sorbitol, polybutadiene acrylic acid acrylonitrile, and poly(methyl methacrylate) along with the manufactured fuel. The experimental results indicate the promise of higher performance using paraffin. The analyses, however, show that refinements in grain design are necessary to fully realize the advantages of paraffin.