Browsing by Author "Dr. Martin King, Committee Member"

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    Design and Development of Superhydrophobic Textile Surfaces
    (2007-03-22) Lee, Hoon Joo; Dr. Stephen Michielsen, Committee Chair; Dr. Trevor J. Little, Committee Co-Chair; Dr. Martin King, Committee Member; Dr. Behnam Pourdeyhimi, Committee Member
    The relationship between contact angles, surface tensions and surface roughness is reviewed. The various numerical formulae related to contact angles were used to predict the surface tension and wetting behavior of polymer surfaces. The apparent contact angle of a droplet deposited on a textured surface is presented, and the characteristics required for a superhydrophobic surface are described. The numerical formulae related to superhydrophilic and superhydrophobic polymer rough surfaces are shown using two approaches, Wenzel and Cassie-Baxter models. Using these models as a guide, artificial superhydrophilic or superhydrophobic surfaces were created. Rough nylon surfaces mimicking the Lotus leaf were created by coating polyester surface with nylon 6,6 short fibers using the flocking process. Poly(acrylic acid) (PAA) chains were grafted onto nylon 6,6 surfaces followed by grafting 1H, 1H-perfluorooctylamine to the PAA chains. Water contact angles as high as 178° were achieved. For a woven superhydrophobic surface, the original Cassie-Baxter model better describes the wetting of rough surfaces. Using mechanical and chemical surface modification of nylon 6,6 woven fabric, artificial Lotus leaves having water contact angles as high as 168° were prepared. Good agreement between the predictions based on the original Cassie-Baxter model and experiments was obtained. However, the version of the Cassie-Baxter model in current use could not explain the wetting behavior of woven fabrics since the surface area fractions in this form is valid only when the liquid is in contact with a flat porous surface. The angle at which a water droplet rolls off the surface has also been used to define a superhydrophobic surface. It is shown that the roll-off angle is highly dependent on droplet size. For our samples, the advancing contact angles of the 1H, 1H-perfluorooctylamine-grafted or octadecylamine-grafted multifilament fabric surface become very close to 180° when the droplet begins to move. However, the receding contact angles are affected by the local structures of fabric such as protruding yarns, yarn size and yarn spacing on the surface. Although the receding contact angles are as small as 90°, the roll-off angles of these superhydrophobic surfaces were less than 5° when a 0.5 mL water droplet was applied.
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    Seamless Textiles with Inherent Shape
    (2005-01-21) Anderson, Kim Suzanne; Dr. George Hodge, Committee Member; Dr. Abdelfattah Seyam, Committee Chair; Dr. Martin King, Committee Member; Dr. Benham Pourdeyhimi, Committee Member; Dr. Nancy Cassill, Committee Member
    Currently, the cutting and sewing process is utilized to produce woven products with tailored shape. Unfortunately, there are a number of adverse consequences caused from seams. The goal of this research was to investigate new methods in which a shaped seamless woven product could be produced using current technology. After a thorough review of the literature, two sets of weaving trials were conducted. In the first set of trials three variables were investigated, specifically 1) different pick densities, 2) different weave constructions and 3) yarns with different degrees of shrinkage. Each variable was manipulated to produce differential shrinkage during the fabric finishing process. In addition, the three variables were utilized in different combinations within a tubular construction in an effort to create inherent shape. The second set of weaving trials were undertaken to investigate the correlation between fabric width shrinkage and a given set of fabric construction parameters in order to create inherent shape within the fabric. Establishing a reliable correlation between fabric width shrinkage and a given set of parameters could lead to the design and development of fabrics with many different shapes. It was of additional interest to investigate the ability to design shaped fabrics with similar finished fabric tightness. The same set of parameters utilized in the first set of weaving trials were examined in the second set of weaving trials. A statistical analysis was performed using the results from the second set of weaving trials. The analysis was performed to examine the success of the overall experiment by assessing the contribution each of the three independent variables made to the resulting finished width shrinkage, as well as finished fabric tightness. In addition, the contributions made by the interactions between different combinations of the independent variables were examined with respect to finished fabric width shrinkage and finished fabric tightness. In order for seamless shaped woven fabrics to be produced without performing additional weaving trials, a predictive model was created. The predictive model would allow a designer to utilize the data generated in the second set of weaving trials to estimate the width shrinkage of a given combination variables. This knowledge would enable a designer to create different shapes by utilizing different combinations of the three variables investigated in this study to produce a specific width shrinkage. In order to assess the potential for a speedy adoption of a seamless woven textile with inherent shape, an economic feasibility study was completed. Everett Roger's Model of the Innovation-Decision Process was used as a paradigm to aid in the investigation of the economic potential of a seamless shaped textile. Other important economic issues pertaining to a new successful product adoption were addressed, including cannibalism, manufacturing strategies and marketing opportunities. Utilizing the proposed experimental methods led to a variety of fabrics with inherent shape. A correlation between fabric width shrinkage and a given set of fabric construction parameters was established. The methods developed in this study could be utilized to produce many different fabrics with inherent shape that might be used in a wide variety of applications. Although seamless shaped fabrics were produced utilizing the methods in this study, future research would be necessary. In this research, none of the fabric samples were tested for physical or mechanical properties. Depending on the intended end use, specific tests would need to be executed to ensure that the seamless shaped products possessed the appropriate characteristics. The ability to reproduce specified dimensions would need to be assessed. In addition, a cost analysis would need to be investigated.