Indiana University-Purdue University Indianapolis (IUPUI) / Background. Beam profile non-uniformity of light-curing units (LCUs) may result in suboptimal properties of resin-matrix composite (RMC) restorations. Objectives: The objective of this study was to evaluate the effect of curing-light beam profile of multiple light curing units (LCUs) on the degree of conversion (DC) and micro-flexural strength (μ-flexural strength) of RMC. Methods: Forty-five nano-filled hybrid RMC (Tetric EvoCeram, Ivoclar Vivadent, Amherst, NY) specimens were fabricated. Quartz tungsten halogen (QTH) (Optilux 401) (O), multiple emission peak (VALO Cordless) (V) and single emission peak (Demi Ultra) (DU) light-emitting-diode (LED) LCUs were investigated at different light-curing locations (LCLs): 1) the center of the LCU tip; 2) 1.5 mm to the left of the center of the LCU tip; and 3) 1.5 mm to the right of the center of the LCU tip. Specimens were stored wet in deionized water at 37C for 24 hours. The DC was measured on top and bottom surfaces using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy. Micro-flexural strength testing was performed using a universal mechanical testing machine at crosshead speed of 1 mm/min. Multi-factorial ANOVAs were used to analyze the data (α = 0.05). Results: All LCUs exhibited significant differences in DC between top and bottom surfaces at the different LCLs. Micro-flexural strength varied with LCL for DU. Conclusions: The non-uniform curing-light beam profile could have a significant effect on μ-flexural strength and DC on top and bottom surfaces of RMC specimens cured at different LCLs.

his thesis deals with preparation of transparent ceramic sheets made out of sub-µm alumina powder. Green bodies are prepared by ultraviolet (UV) curing of UV curable resin containing ceramic powder followed by debinding of organic parts at elevated temperature. High relative density of green bodies is essential for reduction of shrinkage during subsequent sintering process. Therefore high solids loading dispersions containing > 57 vol% ceramic particles are used. To reach transparent behaviour, porosity within the sheets must be reduced completely. Therefore hot isostatic pressing (HIP) is used as a final operation. Finally, light transmission and hardness measurements are presented. Possibilities of making high resolution microstructures using maskless lithography and some suggestions for use of the UV curing technique for production of complex-shaped 3D structures are briefly mentioned.

The ham mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) is the predominant pest of dry cured hams during aging in the processing facilities. Methyl bromide is currently the only known fumigant that is effective at controlling ham mite infestations in aging houses. However, methyl bromide is being phased out of all industries and will be depleted in the near future. The research objectives were to 1) evaluate dry cured hams that have been treated with previously developed food grade coatings for sensory differences, and 2) to develop and determine the efficacy of ham nets incorporated with food grade coatings on controlling mite infestations and sensory properties. Food grade coating combinations of 1) propylene glycol (PG), xanthan gum, and water or 2) PG, propylene glycol alginates, carrageenan and water were dipped and sprayed on whole hams in commercial facilities in the summers of 2014 and 2015 (composition patent pending). The lowest concentration of propylene glycol needed to control mites in laboratory studies was 15% with xanthan gum and 7.5% with propylene glycol alginate and carrageenan. Sensory difference from control tests with trained panelists indicated that there were slight to moderate differences detected in some of the treated hams in comparison to untreated control hams (P < 0.05) when hams were dipped with coatings. However, there were no differences (P > 0.05) detected between the treated hams and the control hams when hams were only sprayed rather than dipped with these coatings. Polyester/cotton blend or cotton nets were infused with various food grade coatings and evaluated on the bench top by inoculating 20 adult mites onto one inch ham cubes for their efficacy at controlling mite infestations. Live adults and mobile immature stages were counted after 14 d of incubation (23 ± 2 °C and 70 ± 5% RH). Mite infestation tests demonstrated that coatings and coating-treated nets were effective at controlling mite growth. Therefore, food grade coatings can be applied to dry cured hams and also can be infused into nets as a potential means to control mite growth in ham processing facilities.

Carbon nanotubes (CNTs) were dispersed into polyvinyl acetate (PVAc ) adhesive cured by radio frequency (RF) to investigate their loading effects on PVAc adhesive curing time and lap shear bond strength performance. Main factors are CNT loading (0.08, 0.25 and 0.41%), RF curing time (15, 30, 45, 60 seconds), and clamping pressure (100, 160, and 240 psi). Experimental results indicated that CNT loading had significant effects on PVAc curing time and lap shear bond strength. Specifically, single lap shear joints bonded with 0.41% CNT loading adhesive had significantly higher lap shear bond strengths than one with PVAc only (0% CNT loading). The curing time of PVAc dispersed with a 41% CNT loading (15 seconds) was 30 seconds shorter than the one with a 0% CNT loading (45 seconds).

No description available.

The curing characteristics of photopolymer resin determine the relationship between the vat polymerization (VP) process parameters and the layer thickness, geometric accuracy, and surface quality of the 3D printed specimen. Dispersing filler material into the photopolymer resin changes its curing characteristics because the filler scatters and absorbs light, which modifies the curing reaction. However, the ability to cure photopolymer resin with high filler volume fraction is important to 3D print material specimens for specific engineering applications, e.g. structural polymer composite materials, electrical and thermal conductive materials, and ceramic materials for biological and high-temperature environments. We methodically measure the curing characteristics of diacrylate/epoxy photopolymer resin with dispersed glass microspheres. The experiments show that the curing depth, degree-of-cure, and surface roughness depend on both the light exposure dose and the filler fraction. We determine that the degree-of-cure increases with increasing filler fraction for constant exposure dose, and approaches 90% with increasing exposure dose, independent of the filler fraction. The geometric accuracy of the 3D printed specimens decreases with increasing exposure dose and with increasing filler volume fraction due to so-called profile broadening. Finally, we show that the average surface roughness of the 3D printed specimens decreases with increasing exposure dose and filler fraction. This work has implications for VP of photopolymer resins with high filler fraction. / Master of Science / Photopolymer resin is a gel-like liquid material that hardens (cures) into solid after absorbing light energy, and such a material is often used in the field of additive manufacturing (3D printing) to create complex geometry. Certain types of filler materials, such as metal powder or carbon fiber, can be added into the photopolymer resin to tailor the material properties, and thus, affects the curing behavior of photopolymer resin mixed with these filler materials. We conducted an experiment to understand how adding glass microspheres to a consumer grade photopolymer resin affects the process of creating 3D objects. This is important in the context of 3D printing engineered composite materials that derive their function from the organization and orientation of filler material in a matrix. To do this, we created many samples in the shape of a "VT" logo using the composite resin we made and measured their thickness (curing depth), degree-of-cure, surface roughness, and geometric accuracy, as a function of the amount of light energy being exposed to the resin (exposure dose) and the amount of the glass filler being added into the resin (filler fraction). We observed that when we increased the amount of light exposure, it resulted specimens that are thicker and more in degree of cure. Adding the glass filler to the liquid had mixed effects on the hardening process, because glass can scatter light and change how light travels within the resin. As a result, the printed objects became less accurate in shape and have smoother surface with increasing exposure dose and filler fraction, because more light is scattered off the designed curing profile and unintentionally cured the surrounding resin.

No description available.

This work describes how a fatty acid methyl ester (FAME) derived from a vegetable oil can be introduced as reactive diluent in a solvent-borne thermally cured coil-coating system. The evaluated reactive diluent, rape seed methyl ester (RME), has been evaluated both in a fully formulated clear coat system and via model studies. A reactive diluent is a compound that acts as a solvent in the liquid paint, lowering the viscosity, and chemically reacts into the final film during cure. Introduction of a reactive diluent derived from vegetable oil give a more environmental compliant coating since a renewable material is incorporated in the coating and the amount of traditional solvent can be decreased. These positive environmental factors have increased the industrial interest. The fully formulated clear coat studies describes how addition of reactive diluent affects rheological properties of the wet paint, film formation, incorporation, and final film properties in a hydroxyl-functional polyester/melamine coil-coating system. The coating were cured under industrial coil-coating cure conditions and analyzed with Raman, carbon-14 dating, extraction, dynamic mechanical analysis, and visually observed. Viscosity measurement of the wet paint show that RME works as a diluent. RME increase the mobility in the system enhancing the film formation process and occurrence of defect-free films. The incorporation of RME could not be confirmed by Raman analysis. However, carbon-14 dating did indicate the presence of RME that could not be extracted from the films. The appearance and mechanical properties of the films were also significantly affected by addition of RME. Dynamic mechanical analysis of the free standing films showed that the final film properties were affected by oven temperature, choice of co-solvent, and flash-off period. Model studies were performed to further clarify how RME chemically can react through transesterification with the hydroxyl-groups of the polyester. RME and its two main components methyl oleate and methyl linoleate were reacted with primary alcohols with and without tertiary hydrogen both under low temperature (110, 130, 150, 170°C) and industrial cure conditions. The transesterification reaction was monitored with 1H-NMR and real time IR. Evaporation and side reactions, e.g. oxidation, are competing factors with the transesterification reaction. The fatty acid structure affects the conversion as a higher amount of unsaturations triggers higher degree of oxidation. The study also showed that reaction time and temperature affects the transesterification conversion, degree of side reactions, and catalyst choice. / QC 20101117

Silicone hydrogels are receiving considerable interest due to their important biomedical application areas such as contact lenses and wound dressings. The applications of such materials are usually in the hydrated state, as hydrogels. However, manufacturing and molding processes are mostly carried out in the organically solvated state, as organogels. This thesis investigates the effects of some of the manufacturing parameters such as curing time and thermal processing on thermal, mechanical, viscoelastic and adhesive/cohesive fracture properties of silicone semi-interpenetrating polymer network organogels. Curing time may affect the extent of reaction and the crosslink density of a gel network. In order to investigate the effect of this parameter, materials were photo-cured for different times within the range of 150s to 1800s. Gel content, uniaxial tensile, dynamic mechanical, adhesive fracture and cohesive fracture properties were obtained as a function of photo-curing time and results were correlated with each other in order to have a better understanding of the effects on the material properties. Additionally, thermal properties of the gels were studied in detail. Crystallization and melting behavior of one of the solvents in the organogel were investigated by differential scanning calorimetry and thermal optical microscopy. Correlation between the thermal properties of the solvent and the gel network structure was shown. Dynamic mechanical analysis experiments were performed to investigate the effect of solvent crystallization on the mechanical properties. Finally, the effect of thermal processing parameters such as the heating  rate and the minimum cooling temperatures on the crystallization and the thermo-mechanical properties were studied. / Master of Science

Yes / This paper examines the impacts of clay mineralogy on the effectiveness of lime stabilisation at different temperatures. A comprehensive experimental programme was conducted to track down the evolution of lime-clay reactions and their durations through monitoring the evolution of strength gain at predetermined times using the Unconfined Compressive Strength (UCS) test. The study examined clays with different mineralogy compositions comprising Na+ Bentonite and Ball (Kaolinite) clay. Four different clays were tested including 100% bentonite, 100% Ball clay and two clay mixtures with ratios of 1:1 and 1:3 by mass of bentonite to Ball clay. All clays were treated using a range of lime content up to 25% and cured for a period of time up to 672 h at two different temperatures of 20 and 40 °C. The results showed that the continuity of the fast phase (stage 1) of strength gain was dependent on the availability of lime in particular at the higher temperature. Whereas, for the same lime content, the duration of the fast phase and the kinetic of strength gain were significantly related to the clay mineralogy and curing temperature. Except for the initial strength gain at 0 h curing time, the lime-treated Ball clay specimens at 20 °C appeared to show no strength gain throughout the curing period that extended up to 672 h. However, when curing occurred at 40 °C, the no strength gain stage only lasted for 72 h after which a gradual increase in the strength was observed over the remaining curing period of time. The addition of Bentonite to Ball clay succeeded in kicking off the strength gain after a short period of curing time at both curing temperatures.