Browsing by Subject "Silicone"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item 3D Printing and Mechanical Performance of Silicone Elastomers(2019-11) Holzman, Noah3D printing of soft, elastomeric materials has potential to increase the accessibility while decreasing the cost of customizable soft robotics and biomedical devices. In this work, the steps to building a 3D printer capable of printing with an extrudable liquid are described. A moisture-cure room temperature vulcanizing (RTV) silicone elastomer was 3D printed. The relative density of printed specimens was determined as a function of infill density specified in the software and the relationship was found to be non-linear and dependent on the sample geometry. Printed test specimens with a range of infill densities and several infill geometries were characterized under uniaxial tension and compression. In tension, the stress-strain behavior is non-linear over the entire curve. Ultimate tensile strength was relatively unaffected by infill density over a range of relative densities from 0.35 to 1.0, while extension at break decreased with increasing infill density. The apparent Young’s modulus was determined in the small-strain limit and is tunable from 310-1150 kPa by adjusting the infill density. Tensile strength of fully-dense printed samples (1150±30 kPa) is comparable to that of the bulk cast samples (1150±40 kPa), indicating good performance of the printing process and few defects. In compression, three different infill patterns and a range of infill patterns were tested. The specimens exhibit stress-strain behavior typical of foams—a linear elastic region with a modulus dependent on infill density, followed by a buckling plateau region and densification at high strains. Negative stiffness due to snap-through buckling was observed in some cases. Results for both tension and compression tests show the tunability of mechanical response achievable through changing the software infill density.Item Lubricity of biomedical conduits(2013-12) Turner, Thomas JamesThe research is motivated by the need to explore the inputs and mechanisms responsible for the creation of beneficial tribological coatings on medical grade silicone rubber tubing and how to quantify them. Despite the fact that biomedical conduits are routinely made lubricious by a host of different methods, there is an insufficiency in the present state of knowledge with regard to how to precisely quantify conduit bore lubricity. Test methods, newly invented, to characterize tubing bore lubricity are described in detail with greater emphasis on the extraction of coefficients of friction relative to historical testing methods. A new invention for characterizing the lubricity of biomedical conduits makes use of a pressure cuff or air-bladder to compress a plasma-treated silicone tubing sample onto a friction element. The instrument setup is a metal sliding-friction-element/silicone- tubing system. The tubing is stationary while the friction element that has been inserted into the tubing bore is pulled. The tubing is held in place with a known and regulated pressure, which allows the normal force pressing on the sliding component to be known. The pull force (tangential force) is registered and recorded using a commercial pull-test frame. Knowing the normal and tangential forces means that the coefficient of friction for the system can be extracted using this instrument.The running-in behavior observed during biomedical conduit friction assessment is quantified and a hypothesis regarding its source is set forth. The theme of the hypothesis is that material related to the constituents of silicone rubber is taken up by the friction element (coil, in this case) over several test cycles and thereby alters the system until it stabilizes. Subsequently, the coil becomes equilibrated with the chemical makeup of its environment, and this is why the resistance force stabilizes. The results of extensive experimentation showed that pristine coils displayed markedly more running-in phenomenon when compared to either an exercised coil or a stored-in-silicone tubing coil.The outcome of the thesis is a thorough understanding of tubing bore lubricity quantification.Item Studies in Sustainable Polymers: Strategies for Feedstock Incorporation and Enhanced Polymer Si–O Bond Cleavage(2022-09) Gormong, EthanThe development of sustainable polymers is a significant undertaking and is best accomplished using a wide variety of complimentary techniques and chemical approaches. The body of work put forth by the NSF Center for Sustainable Polymers embodies this style of collaborative research, aspects of which will be summarized in Chapter 1. A promising avenue toward sustainable polymers is the development of new monomers derived from renewable carbohydrate resources (Chapter 2). The isohexides, including isosorbide, isomannide, and isoidide, can be readily converted into their corresponding bis-propargyl ethers, which can be polymerized using Cu(I) and Ni(II) catalysts. The resulting diyne polymers can be readily converted to their saturated polyether analogs by catalytic hydrogenation. Sustainable polymers are an excellent avenue to excite the next generation of scientists through chemistry laboratory curriculum. Dibutyl itaconate and -myrcene were copolymerized using two different reaction conditions to produce two polymeric materials with vastly different physical properties, suitable for student analysis (Chapter 3). The introduction of degradable linkages into commercial but environmentally persistent polymers, such as silicones, could be an important step toward sustainability. Though usually robust, the Si–O bonds in the polymer backbone can be activated toward cleavage by the introduction of tethered basic functional groups such as dimethyl amides and amines. The effect of tether length of the cleavage of the alkoxydisiloxanes was studied experimentally by 1H NMR analysis of small-molecule analogs and by computation (Chapter 4). These small-molecule findings are currently being applied to other classes of Si–O bonds (carbodisiloxanes) and to macromolecular systems in ongoing research efforts (Chapter 5).