Browsing by Author "Marian McCord, Committee Co-Chair"

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Atmospheric Plasma Characterization and Mechanisms of Substrate Surface Modification
(2007-03-08) Cornelius, Carrie Elizabeth; Mohamed Bourham, Committee Chair; Orlando Hankins, Committee Member; Marian McCord, Committee Co-Chair
The purpose of this research has been to characterize the parameters of an Atmospheric Plasma Device used for surface modifications and functionalization of textile materials. Device parameters are determined in absence and presence of a substrate to quantify the optimal operational conditions. Neutral gas temperature profiles were determined for a variety of gas mixtures including 100% helium and helium with 1 or 2% reactive gases, such as oxygen and carbontetrafluoride. A plasma model was developed to solve for other plasma parameters including the electron-neutral collision frequency and the electron number density. Wool substrates were treated with various gas mixtures for a range of exposure durations and the effects of plasma treatment on weight, surface-functionality, and strength were assessed. Assessment methods include percent weight change calculations, energy dispersive X-ray spectroscopy (EDS), and tensile testing. In addition, cellulosic paper was exposed to 1% oxygen plasma to determine the feasibility of permanently grafting the anti-microbial agent HTCC (quaternized ammonium chitosan). The success of the bond was tested using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), colorimetry, and percent weight change, and the permanency of the bond was tested though soxhlet extraction.
Enhancing Electrostatic Properties and Hydroentangling Efficiency via Atmospheric Plasma Treatment
(2009-08-12) Malshe, Priyadarshini Prakash; Mohamed Bourham, Committee Co-Chair; Marian McCord, Committee Co-Chair; Peter Hauser, Committee Member; Hoon Joo Lee, Committee Member
ABSTRACT MALSHE, PRIYADARSHINI PRAKASH. Enhancing Electrostatic Properties and Hydroentangling Efficiency via Atmospheric Plasma Treatment. (Under the guidance of Professors Marian G. McCord and Mohamed A. Bourham) Keywords: Hydroentangling, atmospheric plasma, nonwoven Hydroentangling is the fastest growing nonwoven bonding technology. Known for the production of most textile-like nonwoven fabric, hydroentangling is a mechanical bonding technique which involves impingement of high velocity water jets onto a nonwoven fiber web. The mechanical action of needle-like water jets entangles fibers and consolidates the web into a fabric. The final properties of a hydroentangled web are reported to depend on the textile material and its intrinsic properties such as strength, modulus, bending rigidity and the fiber surface properties such as friction, fiber shape etc. Hydroentangling efficiency is also shown to depend on fiber to water interaction by way of hydraulic drag force. In previous works by other research groups, water pooling problem has been reported when hydroentangling hydrophobic fibers such as polypropylene. The focus of this work is to eliminate the problem via atmospheric plasma treatment prior to hydroentangling. The purpose of this study is to determine the effects of atmospheric plasma pre-treatment on nonwoven webs due to plasma induced hydrophilicity and other surface modifications such as roughness/smoothness. Different fiber substrates were treated with atmospheric plasma in a continuous run and hydroentangled at different times post-plasma treatment to determine the effect of aging on hydroentangling efficiency.
Responsive Biomaterial Surfaces
(2006-07-26) Wang, Xiaoling; Sam Hudson, Committee Co-Chair; Lola Reid, Committee Member; Marian McCord, Committee Co-Chair
Responsive biomaterial surfaces were fabricated by grafting stimuli-responsive polymers onto polymer material surfaces via a novel Atmospheric Plasma Treatment (APT). They have potential uses in cell adhesion/detachment control, tissue engineering, medical device, drug delivery, bioreactor, bioseparation, and responsive clothing. Temperature sensitive poly(N-isopropylacrylamide) (PNIPAM) was grafted onto various substrates via two novel methods using APT, i.e., atmospheric plasma treatment followed by free radical graft copolymerization (two- step method), and atmospheric plasma treatment of a NIPAM monomer coated surface (coating method). The substrates included nylon film, non-tissue culture treated polystyrene (PS) plates, and cotton fabrics. FTIR confirms the grafting of PNIPAM. The addition of Mohr's salt in the two-step method suppresses homopolymerizaiton and enhances graft yields. The contact angle of PNIPAM-grafted polymer surfaces increases dramatically at ca. 32oC, indicating the temperature sensitivity of the grafted surface, i.e., the change of surfaces from hydrophilic to hydrophobic as temperature increases. Atomic Force Microscope (AFM) shows different topography of original, plasma treated, and PNIPAM grafted surfaces. For the first time, AFM was employed to characterize the grafted surface topography upon changes from dry to wet conditions and from below to above the LCST of PNIPAM. The grafted surface is rough when dry at 22oC, and smooth when wet at 22oC. However, the surface becomes rough again in water at 40oC in response to conformation changes in the PNIPAM hydrogel. Human epithelial cell line HEPG2 cells adhere and proliferate on PNIPAM grafted PS plates at 37oC as on tissue culture plates. However, they detach from the surface automatically at 0oC because of the phase change of PNIPAM. The detachment of HEPG2 cells upon cooling down can be used to recover continuous sheets of tissues from a bioreactor. The tensile property of PNIPAM grafted cotton fabrics was studied. The grafting of PNIPAM still have good tensile property. Comfort test shows thermal sensitivity of the PNIPAM grafted cotton. At 10oC in wet conditions (sweating), less heat transfers from the skin model through the grafted cotton than through the original cotton (control); however at 35oC, more heat transfers from the skin model through the fabric than control. pH responsive Poly(acrylic acid) (PAA) was also grafted on the nylon surface via atmospheric plasma treatment two- step method. The FTIR and water contact angle confirmed the grafting. Compared with conventional vacuum grafting methods, the APT method has several advantages, including no vacuum requirement, low cost, availability to be integrated into a continuous process, and no effect no bulk properties. The APT coating method is especially suitable for industry continuous process.
Stain Repellent-Antimicrobial Textiles via Atmospheric Plasma Finishes
(2008-04-26) McLean, Robert II; Marian McCord, Committee Co-Chair
This research was aimed to impart antimicrobial and stain repellent finishes to polyester fabrics using atmospheric pressure plasma-aided graft copolymerization of active monomers. The process consists of multiple steps; first, surface activation of fabric samples via atmospheric pressure plasma, followed by polymerization reaction of glycidyl methacrylate (GMA) and a quaternary ammonium chitosan derivative (HTCC) compound to produce polyester⁄GMA⁄antimicrobial agent. Next perfluorodecyl acrylate is bound to the polyester⁄GMA⁄antimicrobial agent via polymerization reaction in atmospheric pressure plasma. Samples were exposed to plasma, which has 99% helium and 1% oxygen, for times up to 2 ½ minutes with incremental exposure times to determine the optimal exposure to plasma. Samples were conditioned in an environmental chamber prior to plasma exposure. Weight changes were recorded to determine the percent add-on in each step. Samples were analyzed post plasma exposure and inclusion of the active agents using Scanning Electron Microscopy (SEM) and Energy dispersive X-ray spectroscopy. Standard washing tests were conducted to determine the effectiveness of grafting after washing. Antimicrobial assays and stain repellent tests were conducted on treated samples and compared to control.