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Sustainability has been a driving factor in the recent development of protective coating systems, from reducing volatile organic compounds (VOC’s), integrating biomass for the replacement of petrochemicals, to reducing the number of synthetic or processing steps within a coating system. Incorporating changes to established technologies requires research initiatives focused on matching or exceeding performance properties while maintaining or lowering costs. As a result, sustainable changes to protective coating systems have been under heavy investigation as market demands shift from petrochemicals to renewable materials. This research focuses on the development of unique thermoset coating systems and sustainable improvements. The first study explores the hydrolytic stability between a silanol and an isocyanate, a frequently used reaction that has been relatively understudied. Incorporation of potential hydrolytically unstable silyl carbamates into polyurethane systems may decrease the crosslinking efficiency of the overall network, negatively impacting coating performance. As a result, investigation into the stability of silyl-carbamates may prevent further inefficiencies by eliminating use of this chemistry within polyurethane systems. The second study focuses on the development of alkoxysilane sol-gel consolidants for the protection of stone materials. Sustainable approaches to consolidant formulation include the reduction and elimination of solvent while improving consolidating properties through material selection. The last two studies focus on the incorporation of lignin-derived vanillin into epoxy thermosets and melamine formaldehydes, increasing the overall biobased content of each system. / Office of Naval Research (FAR0025712) / National Center For Preservation Technology and Training, NCPTT (FAR0028305) / EPSCoR/NSF (FAR0030160)

A commercial epoxy, diglycidyl ether of bisphenol-A, was modified by two different routes. One was the addition of silica to produce epoxy composites. Three different silane coupling agents, glycidyloxypropyl trimethoxy silane (GPS), -methacryloxypropyl trimethoxy silane (MAMS) and 3-mercaptopropyltriethoxy silane (MPS), were used as silica-surface modifiers. The effects of silica content, together with the effects of chemical surface treatment of silica, were studied. The results indicate that epoxy composites with silica exhibit mechanical and tribological properties as well as curing kinetics different than the pure epoxy. The optimum silica content for improved mechanical and tribological properties (low friction coefficient and wear rate) was different for each type of silane coupling agent. An unequivocal correlation between good mechanical and improved tribological properties was not found. Activation energy of overall reactions was affected by the addition of silica modified with MAMS and MPS, but not with GPS. The second route was modification by fluorination. A new fluoro-epoxy oligomer was synthesized and incorporated into a commercial epoxy by a conventional blending method. The oligomer functioned as a catalyst in the curing of epoxy and polyamine. Thermal stability of the blends decreased slightly at a high oligomer content. Higher wear resistance, lower friction coefficient and higher toughness were found with increasing oligomer content; thus in this case there was a correlation between good mechanical and improved tribological properties. The results indicated that increasing toughness and formation of a transfer film contribute to improved tribological performances.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Construction with composite materials has become increasingly popular in contemporary structural design for multi-storey residential, commercial, and industrial buildings. As a composite structure, pre-stressed heavy timber buildings offer sustainable, environmentally-friendly advantages over competing construction technologies utilising structural steel and concrete components. Research at the University of Canterbury is continually investigating the performance and behaviour of this composite heavy timber construction assembly. The following research report provides a fire resistance analysis for pre-stressed heavy timber structures that includes: • A comprehensive literature review detailing the fire resistance for pre-stressed heavy timber structural components and typical connections; and • A four-phase series of experiments with epoxy grouted steel threaded rods and proprietary mechanical fasteners to determine the fire resistance properties of steel to wood connections. Laboratory experimentation includes cold testing to determine connection performance at ambient temperature, oven testing to evaluate heating effects on steel to wood connections, cooled testing to determine the residual strength of connections in minor fires and, finally, furnace testing to generate fire resistance design and analysis equations to be utilised for steel to wood connections. Recommendations for the fire performance of connections in pre-stressed heavy timber structures are included in the report.

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No description available.

In this study, glass and Kevlar® fibers reinforced epoxy composites were manufactured and characterized using different techniques. The effect of thermal exposure on the flexural properties of the composites was investigated to ascertain its suitability for the intended application in cowling panels of light engine aircraft. Thermogravimetric analysis (TGA) was carried out on both reinforced and unreinforced epoxy resin to evaluate their thermal stability at elevated temperatures. Dynamic mechanical thermal analysis was carried out to evaluate the effects of thermal exposure, applied strain and frequency on the dynamic mechanical response of the composites. The effects of the applied resin hardener and thermal exposure on the flexural strength, flexural modulus and dynamic impact response of the composites were also investigated. The flexural properties were determined using 3-point bending test, while the impact test was carried out using Split Hopkinson Pressure Bar (SHPB). TGA analysis of the reinforced and unreinforced epoxy showed no significant weight loss until the test samples were heated above 250°C in an inert atmosphere. Dynamic Mechanical Thermal Analysis (DMTA) on the composites indicated the glass transition temperature to lie between 80 and 100°C. The results of the flexural and impact tests showed that the mechanical integrity of both glass and Kevlar® fiber reinforced epoxy composites remained unimpaired by radiative or convective heat exposure for up to 3 h until the exposure temperature exceeded 200°C. This is much higher than the service temperature of cowling panels of light engine recreational aircrafts. When the manufactured fiber reinforced epoxy composites were exposed to temperature above 200°C matrix degradation occurred, which became very significant when the exposure temperature was higher than 250°C. Extensive delamination and matrix cracking occurred when the composites were exposed to the temperature range 250°C - 300°C for 1 h. Fiber-matrix debonding was not observed in the composite except after failure under impact loading. This is evidence of the fact that the epoxy matrix was adequately wetted by both the glass and Kevlar® fibers resulting in the strong fiber/matrix interfacial bonding. While the Kevlar® reinforced epoxy displayed a better damage tolerance under flexural and impact loading, glass fiber reinforced epoxy showed higher strength but lower damage tolerance. Glass fiber reinforced epoxy also showed more resistance to damage under exposure to thermal flux than Kevlar® reinforced epoxy. Under impact loading, the Kevlar® reinforced composite failed by delamination with no fiber rupture, whereas the glass fiber reinforced epoxy failed by matrix cracking, debonding, fiber rupture and fiber pullout. The results from this research have established the effect of radiative and convective thermal exposure on the mechanical behavior of the fabricated Kevlar® fiber and glass reinforced epoxy composites. The maximum temperature reached on the inner surface of the cowling panels of a typical light engine recreational aircraft due to heat radiations from the engine block has been estimated to be about 65°C. This is lower than the glass transition temperature of the epoxy matrix as obtained from DMTA. The low temperature rise is due to inflow cooling air into the cowling chamber in flight. The results of the current investigations suggest the suitability of composite materials for the intended application. The intensity of thermal exposure, to which the materials will be exposed in such application, may not cause any significant damage to the mechanical integrity of the composite. However, since the difference between the possible exposure temperature and the glass transition temperature is only a little over 20°C, a layer of thermal insulator on the inner surface of the cowling made of fiber reinforced epoxy will be desirable to further sustain the mechanical integrity of the composites when selected for use as choice materials for cowling panels of light engine aircraft.

This work investigated cathodic disbonding of an unpigmented phenalkamine-cured epoxy coating on mild steel, EC, exposed to 3.5 wt.% NaCl solution. Scanning Acoustic Microscopy (SAM), Scanning Kelvin Probe (SKP), Electrochemical Impedance Spectroscopy (EIS) and optical microscopy have been combined to conduct this study. Several factors affecting the cathodic disbonding process: Film thickness, Cation mobility, Electrolyte concentration, Temperature, Paint composition, Polarisation and Open circuit potential, have been investigated. SAM results show that the disbonding of EC with a linear scribe spreads outwards from the defect with blisters forming at the anodes (as shown in SKP potential maps) within the disbond. The disbonded region does not correspond to complete adhesion loss as verified by peel-testing. Semi-immersion tests show that disbonding under full- and semi-immersion conditions have similar behaviours and both follow parabolic kinetics indicating the disbonding is likely to be controlled by a transport process along the coating/metal interface. An intact epoxy coated mild steel panel coupled with bare mild steel shows that the cathodic reaction beneath the coating obeys Tafel law. A mathematical model simulating cathodic disbonding which produces realistic potential files and shows the oxygen reduction is mostly located near the disbond mouth has been developed.

SC-15 epoxy is used in many industrial applications and it is well known that the mechanical and viscoelastic properties of epoxy can be signicantly enhanced when reinforced with nanofillers. In this work, SC-15 epoxy is reinforced by loading with magnetically-active nanofillers and cured in a modest magnetic field. Because of the signicant magnetic response of the nanofillers, this is a low cost and relatively easy technique for imposing a strong magnetic anisotropy to the system without the need of a superconducting magnet. It is also found that this method is an effective way of enhancing the mechanical properties of epoxy. Three systems were prepared and studied. The first is a dilute system of various concentrations of Fe2O3 nanoparticles in SC-15 epoxy. The second system is a combination of Fe2O3 nanoparticles and chemically-functionalized single-walled carbon nanotubes (SWCNT(COOH)s) in SC-15 epoxy. The third is a dilute system of SWCNT(COOH)s decorated with Fe3O4 particles t hrough a sonochemical oxidation process in SC-15 epoxy. Samples have an initial cure of 6 hrs in a magnetic led of 10 kOe followed by an additional 24 hours of post curing at room temperature. These are compared to the control samples that do not have initial field curing. Tensile and compressive stress-strain analysis of the prepared systems shows that mechanical properties such as tensile strength, tensile modulus and compressive strength are enhanced with the inclusion of these nanofillers. It is also found that there is an anisotropic enhancement of these properties with respect to the imposed curing field. An interesting phenomenon is observed with the increase in modulus of toughness and fracture strain with nanotube inclusion. / These parameters are drastically enhanced after curing the systems in a magnetic field. While there is a modest shift in glass transition temperature during viscoelastic analysis, the thermal stability of the created systems is not compromised. Results of these mechanical enhancements will be compared with other nanoloading techniques from literature. / by Olga Malkina. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.