Thesis (PhD) -- University of Western Sydney, 2002. / "A candidate for the degree of Doctor of Philosophy." "A thesis submitted in the School of Science, Food and Horticulture, University of Western Sydney." "June 2002" Bibliography: leaves 303 - 305.

abstract: The alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts have been extensively studied due to the advantages they offer in terms enhanced material properties, while increasing sustainability by the reuse of industrial waste and byproducts and reducing the adverse impacts of OPC production. Fly ash and ground granulated blast furnace slag are commonly used for their content of soluble silica and aluminate species that can undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification. The following topics are the focus of this thesis: (i) the use of microwave assisted thermal processing, in addition to heat-curing as a means of alkali activation and (ii) the relative effects of alkali cations (K or Na) in the activator (powder activators) on the mechanical properties and chemical structure of these systems. Unsuitable curing conditions instigate carbonation, which in turn lowers the pH of the system causing significant reductions in the rate of fly ash activation and mechanical strength development. This study explores the effects of sealing the samples during the curing process, which effectively traps the free water in the system, and allows for increased aluminosilicate activation. The use of microwave-curing in lieu of thermal-curing is also studied in order to reduce energy consumption and for its ability to provide fast volumetric heating. Potassium-based powder activators dry blended into the slag binder system is shown to be effective in obtaining very high compressive strengths under moist curing conditions (greater than 70 MPa), whereas sodium-based powder activation is much weaker (around 25 MPa). Compressive strength decreases when fly ash is introduced into the system. Isothermal calorimetry is used to evaluate the early hydration process, and to understand the reaction kinetics of the alkali powder activated systems. A qualitative evidence of the alkali-hydroxide concentration of the paste pore solution through the use of electrical conductivity measurements is also presented, with the results indicating the ion concentration of alkali is more prevalent in the pore solution of potassium-based systems. The use of advanced spectroscopic and thermal analysis techniques to distinguish the influence of studied parameters is also discussed. / Dissertation/Thesis / M.S. Engineering 2013

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.

Indiana University-Purdue University Indianapolis (IUPUI) / Objective: The objective was to assess a multiple emission peak light-emitting-diode (LED) light-curing unit (LCU) by measuring the polymerization efficiency through the degree of conversion (DC) and Knoop microhardness (KHN) of a resin-based pit and fissure sealant at various light curing times and two distances compared to a single emission peak LED LCU. Method: Sixty disks of resin-based pit and fissure sealant (Delton, DENTSPLY, York, PA) samples (6x1mm) were fabricated (n=5/LCU/group). Prepared samples were polymerized using 10, 20 and 40 second curing time at 2 or 4 mm curing distances. The irradiance and radiant exposure received on the top/bottom surfaces of the samples were measured using the Managing Accurate Resin Curing-Resin Calibrator (MARC-RC) system. The samples were stored at 37°C for one hour. Then, the DC (n=3/surface) and KHN (n=5/surface) measurements were collected on the top and bottom surfaces using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and a microhardness tester (Instron) utilizing 25-gm at 10 seconds dwell time, respectively. Multiple-way ANOVA was performed followed by Tukey test (α=0.05). Result: The irradiance from the multiple emission peak LED LCU was significantly higher than the single emission peak LED LCU (1312.6 and 768.3 mW/cm2) respectively. Moreover, the multiple emission peak LED LCU displayed significantly higher DC (82.5%) and microhardness (26.2 KHN) compared to the single emission peak LED LCU (75.5% DC and 21.2 KHN) when curing samples at 2 and 4 mm curing distances assessed using 10, 20 and 40-second curing times. The 10 second cure at 4 mm showed significantly lower DC and KHN values compared to the other groups. Conclusion: The multiple emission peak LED LCU demonstrated significantly higher irradiance, DC and KHN compared to the single emission peak LED LCU on a resin-based pit and fissure sealant at 2 and 4 mm curing distances and 10, 20 and 40 second curing times. Therefore, the multiple emission peak LED LCU performed higher than the single emission peak LED LCU.

An adaptation of an extrinsic Fabry-Perot interferometer (EFPI) strain sensor is described, which permits the state of cure of an epoxy matrix to be monitored, when the sensor is embedded in a polymeric matrix composite. By using a glass rod with a retroreflecting end for the target fiber in the EFPI sensor, the intensity of the light reflected depends on the refractive index of the host matrix, if a low coherence source is used. As the epoxy cross-links during cure, the refractive index of the epoxy will increase to a value exceeding that of the target fiber. The resulting increased loss in the fiber can be detected at the sensor output and correlated to the state of cure of the epoxy. After cure, the sensor may be operated as a conventional extrinsic Fabry-Perot interferometric strain sensor if a coherent source is used. Using the modified extrinsic Fabry-Perot sensor, we monitor the cure of Devcon® 5-Minute® Epoxy, and show that it cures in approximately 60 minutes. / Master of Science

The state of cure of epoxies is an important issue in the manufacture of graphite epoxy composites used in aerospace structures. Variations in the initial state and process used to cure the epoxy resin in a composite material lead to variations in the mechanical properties of the part manufactured from the composite._[12] Control of these variation can be accomplished by monitoring the bulk and shear moduli of the epoxy resin as it cures. The moduli properties of the resin determine the acoustic properties of the epoxy._{[12],[13],[14]} Hence measurement of the acoustic longitudinal velocity and attenuation of the epoxy during its cure cycle provides a good indicator of the state of cure. Optical fiber waveguides can be embedded within a host material and used to detect longitudinal acoustic waves._[15],[16] Herein, the mechanisms allowing the detection of ultrasound with optical fiber are presented. An analysis of optical fiber waveguides and optical fiber based interferometric detection methods is performed in detail. The interaction of radial strain fields, induced by longitudinal acoustic waves, with singlemode optical fibers is described. Experimental results obtained in epoxy cure monitoring, using an optical fiber based method for acoustic detection, are compared with results obtained using conventional piezoelectric based acoustic detection methods. / Master of Science

Thesis (M. Tech. - Engineering: Electrical, Department Electronic Engineering, Faculty of Engineering and Technology)--Vaal University of Technology. / Curing of materials in order to obtain different properties has been a practice for many years. New developments in composite materials increase the need to control certain variables during the curing process. One very significant variable is temperature. Temperature control by itself is an old practice, however when the need for repeatedly controlling the process accurately over long periods of time arises, a system is required that outperforms normal manual control. One of the aspects within such a system that needs to be considered is the ability to replicate the temperatures within an oven which were originally used for a specific material’s curing profile. This means that a curing profile would need to be defined, saved for later and finally be interpreted correctly by the controlling system. Different control methods were simulated to enable the system to control the temperature which has been defined by literature. This dissertation introduces a variation on the standard control methods and shows improved results. Switching the oven on and off in order to increase or decrease internal oven temperature seems simple, but can cause switching devices to decrease their operational life span, if not designed carefully. A combination switch was introduced which harnesses the advantages of two very common switching devices to form an improved combination switch. Software for the personal computer environment, as well as software for the embedded environment were developed and formed a control system that produced acceptable results for temperature control. Accuracies of 98% and more were achieved and found to be acceptable according to standard engineering control practices. An accurate temperature profile controller was designed, simulated and built in order to control the temperature inside a specific curing oven which, in turn, determined the curing properties of specific materials. The overall results were satisfactory which lead to achieving the objectives outlined in this dissertation.

Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this study is to further investigate the effect of using six different light source types with different light output intensities on the parameters of a mathematical model that predicts the DOC in VLDC’s. In this equation: D = Dp In(E0/Ec), D is the depth of cure in millimeters, E is the curing energy in J/cm2, Ec is the critical curing energy for the composite to reach a gel layer, and Dp is a characteristic coefficient. Three LED and three halogen dental curing units with different light output intensities were used to cure three shades (B1, A3, D3) of a hybrid resin composite. The exposure duration was at the intervals of 10, 20, 30, and 40 seconds for each sample setting. ISO scraping technique was performed to measure the depth of cure of each sample. Regression analysis was used to assess the fit of the proposed mathematical model D = Dp In(E0/Ec) to the experimental data obtained in this study. 72 For all the shade-light combinations; A3, B1, and D3 had significantly different regression lines (P < 0.05) with significantly higher Dp and Ec for B1 than A3 and D3. The only exceptions were for the Ec values between B1 and D3 in Allegro, Astralis 5, and Visilux 2 groups; and the Ec between A3 and B1 in Allegro group. The Dp and Ec parameters didn’t show significant differences between A3 and D3 shades in all the groups. Also, most of the significant differences for Dp values occurred in the B1 shade-light combinations; however, none of the D3 shade-light combinations showed significant differences for Dp. Several factors play combined influential effects on the kinetics of polymerization and depth of cure in VLDC’s. The shade has a more dominant effect on both parameters Dp and Ec than the curing light type or source output intensity. As we cure lighter shades “B1,” the effect of using different lights with different output intensities on the two parameters Dp and Ec will be greater and more significant than for darker shades “A3 or D3.” The clinical significance drawn from this study is that clinicians should recognize that using curing lights w/ increased output intensities doesn’t absolutely increase the DOC of VLDC’s especially with the darker shades.

Research was initiated to examine the feasibility of removing the majority of 4-PCH from the XSBR latex employed in carpet manufacturing. The reduction of 4-PCH from such latices would lend insight into the control of certain carpet related illnesses.

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 1994. / This thesis presents the details and results of an investigation into the effects of early age curing on the durability of concrete The two main objectives of the investigation were: to develop simple test methods, applied at relatively early ages, for measuring the effects of early-age moist curing on the advance of hydration in the cover zone of concrete; to quantify the effect of early age curing on the durability performance of concretes of various strength grades and made with different binder types. [Abbreviated Abstract. Open document to view full version]