Concentration of microorganisms from a sample volume would increase the limits of detection of samples used for rapid-detection methods. Rapid detection methods are is advantageous for the food industry to rapidly test for bacteria in order release products on a timely basis. Ultrasonic concentration was considered a promising method for manipulation of microorganisms. An ultrasonic chamber consisting of parallel piezoceramic discs with a reticulated polyurethane foam mesh was used to concentrate Saccharomyces cerevisiae yeast and Escherichia coli bacteria. The concentration of yeast was seen to increase by 200% (from 8.0 x 104 cells mL-1 to 2.4 x 105 cells mL-1) while almost zero concentration of bacteria was observed. The poor concentration effect seen with the smaller microorganisms was explained by the volume dependent acoustic radiation force exerted on the particles; the concentration forces are 1,000 times smaller for a 1 μm bacteria cell versus a 10 μm yeast cell.

The ignition and subsequent burning of polyurethane foam based mattresses poses a significant danger to life and safety in North American homes. The development of fire models which can predict the full scale fire behavior of these mattresses using bench scale data would assist manufacturers and regulators to manage this danger in a cost effective manner. This thesis builds on previous work by the University of Saskatchewan and University of Waterloo fire research groups and focuses on the evaluation of one such scaling model, which was originally developed during the Combustion Behavior of Upholstered Furniture (CBUF) project. The evaluation of the CBUF model conducted in this thesis isolates the heat release rate (HRR) density sub-model and explores the effects of 1) cone calorimeter incident heat flux setting, 2) specimen thickness and 3) ignition location on the predictive capability of the CBUF model. To provide input for the CBUF model cone and furniture calorimeter tests were conducted. Cone calorimeter tests were conducted on foam specimen thicknesses of 2.5, 5.0, 7.5 and 10.0 cm at incident heat flux settings of 25, 35, 50 and 75 kW/m2. Furniture calorimeter tests were conducted on foam specimen thicknesses of 2.5, 5.0, 7.5 and 10.0 cm in both edge and center ignition configuration. Flame area spread rates were measured from infrared video of the furniture calorimeter tests using an automated algorithm. It was found that HRR curves predicted by the CBUF model showed good agreement with experimental results. Experimental results from tests of thinner foams were predicted with greater success than results from thicker foams, and results from edge ignition tests were predicted with greater success than results of center ignition tests. The results of this study indicated that specimen thickness and ignition location need to be considered when selecting an appropriate incident heat flux setting for producing input data for the CBUF model.

A degradable/polar/hydrophobic/ionic (D-PHI) polyurethane with properties intended to promote tissue regeneration in a small diameter peripheral artery vascular graft was evaluated for cell biocompatibility and growth. Films were cast in polypropylene 96 well plates for monocyte/endothelial cell (EC) co-culture in vitro studies and porous scaffold discs were implanted in an in vivo subcutaneous mouse model. After 7 days in culture the co-culture demonstrated cell adhesion and growth, low esterase activity (a measure of degradative potential and cell activation), no detectable release of pro-inflammatory cytokine (tumour necrosis factor -α) but measurable anti-inflammatory interleukin (IL)-10. The EC and the co-culture expressed the EC biomarker CD31, whereas the monocyte monoculture did not. Cytokine array analysis of the in vivo characterization of D-PH supported an anti-inflammatory phenotype of cells at the site of the implant. Levels of IL-6 significantly decreased over time while IL-10 was significantly higher at 6 weeks post implant. TNF-α levels did not change significantly from 24 hours onwards, however the trend was towards lesser amounts following the initial time point. Histological analysis of the explanted scaffolds showed excellent tissue ingrowth and vascularization. A live/dead stain showed that the cells infiltrating the scaffolds were viable. Both the in vitro and in vivo results of this thesis indicate that D-PHI is a good candidate material for tissue engineering a peripheral artery vascular graft.

Injection molding technology is utilized for a wide range of applications from mobile phone covers to bumper fascia of automotive vehicles. Foam injection molding (FIM) is a branched manufacturing process of conventional injection molding, but it was designed to take advantage of existing foaming technology, including material cost saving and weight reduction, and to provide additional benefits such as improvement in dimensional stability, faster cycle time, and so on. Gas-assisted injection molding (GAIM) is another supplemental technology of injection molding and offers several advantages as well. This thesis study takes the next step and develops innovative gas-assisted foam injection molding (GAFIM) technology, which is the result of a synergistic combination of two existing manufacturing technologies, FIM and GAIM, in order to produce a unique thermoplastic foam structure with proficient acoustic properties. The foam structure manufactured by GAFIM consists of a solid skin layer, a foam layer, and a hollow core; and its 6.4-mm thick sample outperformed the conventional 22-mm thick polyurethane foam in terms of the acoustic absorption coefficient. With respect to foaming technology, GAFIM was able to achieve a highly uniform foam morphology by completely decoupling the filling and foaming phases. Moreover, the additional shear and extensional energies from GAFIM promoted a more cell nucleation-dominant foaming behavior, which resulted in higher cell density and smaller cell sizes with both CO2 and N2 as physical blowing agents. Lastly, it provided more direct control of the degree of foaming because the pressure drop and pressure drop rate was controlled by a single parameter, that being the gas injection pressure. In summary, innovative, gas-assisted foam injection molding technology offers not only a new strategy to produce acoustically functioning thermoplastic foam products, but also technological advantages over the conventional foam injection molding process. Gas-assisted foam injection molding can become the bedrock for more innovative future applications.

Injection molding technology is utilized for a wide range of applications from mobile phone covers to bumper fascia of automotive vehicles. Foam injection molding (FIM) is a branched manufacturing process of conventional injection molding, but it was designed to take advantage of existing foaming technology, including material cost saving and weight reduction, and to provide additional benefits such as improvement in dimensional stability, faster cycle time, and so on. Gas-assisted injection molding (GAIM) is another supplemental technology of injection molding and offers several advantages as well. This thesis study takes the next step and develops innovative gas-assisted foam injection molding (GAFIM) technology, which is the result of a synergistic combination of two existing manufacturing technologies, FIM and GAIM, in order to produce a unique thermoplastic foam structure with proficient acoustic properties. The foam structure manufactured by GAFIM consists of a solid skin layer, a foam layer, and a hollow core; and its 6.4-mm thick sample outperformed the conventional 22-mm thick polyurethane foam in terms of the acoustic absorption coefficient. With respect to foaming technology, GAFIM was able to achieve a highly uniform foam morphology by completely decoupling the filling and foaming phases. Moreover, the additional shear and extensional energies from GAFIM promoted a more cell nucleation-dominant foaming behavior, which resulted in higher cell density and smaller cell sizes with both CO2 and N2 as physical blowing agents. Lastly, it provided more direct control of the degree of foaming because the pressure drop and pressure drop rate was controlled by a single parameter, that being the gas injection pressure. In summary, innovative, gas-assisted foam injection molding technology offers not only a new strategy to produce acoustically functioning thermoplastic foam products, but also technological advantages over the conventional foam injection molding process. Gas-assisted foam injection molding can become the bedrock for more innovative future applications.

Tissue engineering the annulus fibrosus (AF) for use in a functional intervertebral disc replacement is a promising alternative to current treatments of degenerative disc disease. Polycarbonate urethane (PU) scaffolds have demonstrated the ability to support AF cell attachment and matrix synthesis and are suitable for tissue engineering the AF. The present study investigates the effects of the physical and biochemical environment on AF cells grown on aligned nanofibrous PU scaffolds. First, the effect of dynamic spinner flask culture and fibronectin pre-coating on tissue formation was analyzed and then the role of scaffold fibre tension on annulus fibrosus cells was examined using a tailored culture system. The results of these studies demonstrated that AF cells are sensitive to differences in biochemical cues at the scaffold surface and their physical environment and respond by altering their cellular responses and, potentially by manipulating their microenvironments, including the physical characteristics of the PU-ADO scaffolds.

Tissue engineering the annulus fibrosus (AF) for use in a functional intervertebral disc replacement is a promising alternative to current treatments of degenerative disc disease. Polycarbonate urethane (PU) scaffolds have demonstrated the ability to support AF cell attachment and matrix synthesis and are suitable for tissue engineering the AF. The present study investigates the effects of the physical and biochemical environment on AF cells grown on aligned nanofibrous PU scaffolds. First, the effect of dynamic spinner flask culture and fibronectin pre-coating on tissue formation was analyzed and then the role of scaffold fibre tension on annulus fibrosus cells was examined using a tailored culture system. The results of these studies demonstrated that AF cells are sensitive to differences in biochemical cues at the scaffold surface and their physical environment and respond by altering their cellular responses and, potentially by manipulating their microenvironments, including the physical characteristics of the PU-ADO scaffolds.

Significant potential for plastic hypodermic needles exists as an alternative to current steel needles, especially in developing regions where proper needle disposal is problematic. Needle reuse causes tens of millions of hepatitis and HIV infections each year. Plastic needles may reduce reusability and increase the opportunities for safe disposal. Plastic needles also will help with medical waste disposal, by removing metal from the waste stream, hence making it easier to reprocess needles and syringes into useful products such as car battery cases and pails. This thesis presents the design and testing of one type of plastic hypodermic needle. The buckling and penetration characteristics of the needles were modeled and analyzed analytically and by finite element analyses. Experimental penetration tests using steel and plastic hypodermic needles and skin mimics, specifically polyurethane film and pig skin, were performed to determine penetration and friction forces. Penetration tests also were conducted to determine whether the needles could penetrate butyl rubber stoppers that cover drug vials. Various lubricants, including silicone oil and a medical grade silicone dispersion, were also used. In addition, the needles underwent perpendicular bending tests and cannula stiffness tests. Finally, fluid flow tests were conducted to determine fluid flow rates through the needles. Experimental results were compared to each other and finite element analyses and discussed. The research presented in this thesis demonstrates that with further design modifications, plastic needles may become suitable for mass replacement of steel needles, thus helping to eradicate the many health and environmental risks brought upon by steel needles.

The current application of low persistence pesticides is unreliable for protecting wooden structures from termite attack. These applications may also pose an environmental and public health risk. Consequently, there is a need for the development of alternative systems to protect wooden structures from termites. Investigated here is the interaction between Australian termites, Coptotermes acinaciformis Froggatt, and to a lesser extent, Mastotermes darwiniensis Froggatt and Schedorhinotermes seclusus Hill, and a barrier system for protection of wooden structures. The aim was to develop an improved barrier for the protection of wooden structures that maximizes protection and minimizes environmental and health risks. Specifically, the performance of a barrier to protect wood against termite attack that incorporates a synthetic pyrethroid into polyurethane formulations is investigated. This research was conducted in parallel with other project contributors focusing on material science aspects of the research goals. A fundamental problem in assessing the value of termite barrier strategies lies in developing and interpreting laboratory assays that can deliver reasonable predictions of performance in the field. This is particularly the case with respect to the behaviour of termites over much longer periods in the field than can be undertaken in the laboratory. The approach to laboratory trials presented here is to define individual termite capabilities and, in combination with behavioural studies, to develop an understanding of factors which affect termite performance. The key experimental approach involved various laboratory based assays to evaluate termite foraging behaviour and performance against a range of barrier materials, progressing to field trials with the best performing material. Various species of termites; M. darwiniensis (Mastotermitidae), Cryptotermes primus (Hill) (Kalotermitidae), C. acinaciformis , Coptotermes frenchi Hill and S. seclusus (Rhinotermitidae), Microcerotermes serratus (Froggatt), Microcerotermes turneri (Froggatt) and Nasutitermes walkeri (Hill) (Termitidae) and Porotermes adamsoni (Froggatt) (Termopsidae); were investigated to determine the force that they can develop at their mandible tips. Larger termites can generate higher pressures on their mandible tips than smaller termites. By quantifying the mandible strength of a termite it was possible to contrast the capabilities of various economic termite species. Damage caused by an individual termite biting on synthetic materials was measured using electron microscope generated three dimensional models of indentations caused to the material. This was successful in quantifying the immediate capabilities of individual termites of different species. Most species were found to inflict a similar amount of damage to high density polyethylene. However M. darwiniensis caused much more damage than other species examined. Micro hardness testing was utilized to determine the relative hardness of pest termite mandibles. Termites were found to have mandibles much harder than any tested synthetic material. It was therefore found to be unrealistic to aim to develop barrier technology based on “harder than termite mandible material”. Trials using groups of termites in the laboratory demonstrated large differences in the performance of termites against various synthetic materials. There was a tendency for harder materials to suffer less damage. Mechanical properties of the barrier alone were found to be insufficient to stop termite damage. The resistance of polyurethane formulations incorporating insecticides to termite attack in the laboratory demonstrated a potential suitability for termite barrier technology. In behaviour trials, persistence of termite attack at the barrier face was found to be due not only to deterrent chemicals, but also to physical characteristics. Softer materials are not only easier for termites to remove but termites attack softer materials with greater tenacity, more termites spend more time attacking softer materials. Laboratory toxicity trials confirmed the bioavailability of Bifenthrin when incorporated within the barrier material and enabled the establishment of expected concentrations for effective protection. Termites were found to require direct contact with the barrier for mortality to occur. Trials designed to quantify repellence of the Bifenthrin in the barrier found that termites did not escape mortality by avoiding contact with the barrier material. As such pure Bifenthrin is shown to protect the barrier material directly by causing mortality rather than by repelling live termites away from the barrier. Field trials were conducted in northern Queensland where colonies of economic termites could be directly targeted. Wooden blocks were coated in polyurethane containing a range of Bifenthrin concentrations and trialed over an eight month period. Combination of the pyrethroid Bifenthrin in a polyurethane barrier at concentrations as low as 0.07% proved successful in preventing damage by the economically important termites M. darwiniensis and C. acinaciformis under high pressure field conditions. Only very small amounts of Bifenthrin migrated into adjacent soil, concentrations reached were in the order of 100 µg/kg of soil. For comparison the MLR for Bifenthrin in bananas for human consumption is 100 µg/kg. Bifenthrin in a polyurethane barrier could be used for the protection of houses and other wooden structures in the same manner as existing barrier film technology in order to minimise environmental and health risks associated with direct pesticide application techniques.

Zugl.: Stuttgart, Univ., Diss., 2004