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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Characterization of plasma-polymerized polyethylene glycol-like films

Pathak, Shantanu Chaturvedi 25 September 2008 (has links)
A parallel-plate capacitively-coupled plasma deposition system was designed and built for the growth of polyethylene glycol-like films. Deposition rate, bonding structure and dissolution and swelling behavior was characterized as a function of input RF power, reactor pressure and substrate temperature to provide information on the relationship between input plasma parameters and film properties. For the conditions studied in this thesis, deposition rates increased at increasing input powers and operating pressures and decreasing substrate temperatures. The PEG-like coatings resembled higher molecular weight solution-polymerized PEG films with a higher crosslinked structure. Manipulation of plasma deposition conditions allowed control of film crosslink density and resulted in tunable dissolution and swelling properties of the PEG-like polymer. At higher applied powers, lower operating pressures, and higher substrate temperatures, films had a higher crosslink density, thus leading to slower dissolution rates and smaller extents of swelling. Void space openings of swelled-state, PEG-like films were determined using electrophoretic drift and diffusion-controlled transport of fluorophore-tagged PAMAM dendrimers into the bulk of the coating. PAMAM dendrimers were used because of their well-defined sizes and negatively-charged succinamic acid surface groups as a means to probe pore sizes of the plasma films. It was estimated that the upper bound of pore size diameters in the plasma polymer was approximately equal to ~5.5-6.0 nm. Positron annihilation lifetime spectroscopy was used to determine average pore sizes and was estimated to equal ~0.60-0.65 nm.
2

Clinical and economic evidence supporting a transparent barrier film dressing in incontinence-associated dermatitis and peri-wound skin protection

Guest, J.F., Greener, M.J., Vowden, Kath, Vowden, Peter 11 February 2011 (has links)
No / To summarise the clinical and economic literature relating to the effect of Cavilon No Sting Barrier Film on the incidence of incontinence-associated dermatitis, which is a risk factor for pressure ulceration and exudate-related peri-wound skin damage. Method: A systematic literature search was performed using available computerised databases for publications on Cavilon barrier film and other relevant terms. Six clinical studies were identified providing data on 1,563 patients treated with the barrier film or a comparator. The publications comprised prospective studies, randomised and non-randomised studies, multicentre trials, single-centre reports and a volunteer study. Due to the nature of the comparators, five studies were open-label. Differences in methodology and outcomes made a qualitative review the most appropriate analysis. Results: The barrier film was at least as effective as petroleum ointments and more effective than zinc oxide formulations in preventing incontinence-associated dermatitis. The barrier film was also effective in peri-wound skin protection, although its clinical efficacy was not significantly different to that of petroleum ointments and zinc oxide formulations. Nevertheless, the barrier film was more cost-effective than either petroleum ointments or zinc oxide formulations in managing incontinence-associated dermatitis and peri-wound skin protection, largely due to savings in nursing time. Conclusion: The barrier film is at least as clinically effective and potentially more cost-effective in incontinence-associated dermatitis prophylaxis and peri-wound skin protection than petroleum ointments or zinc oxide formulations, releasing health care resources for alternative use. Further studies are required to quantify the relative efficacy and cost-effectiveness of the barrier film and other barrier formulations in different clinical settings and enhance the quality of the evidence base.
3

Functionalized nanocelluloses and their use in barrier and membrane thin films

Visanko, M. (Miikka) 13 October 2015 (has links)
Abstract Nanocellulose is envisioned as one of the key product innovations of future biorefineries, since it can potentially function in numerous high-end applications and replace many current petroleum-based products due to its superior properties, abundance and renewable nature. The main difficulty hindering the industrial upscaling of nanocellulose is the lack of feasible techniques for processing cellulose fibres on a nanoscale. At the same time, ongoing research efforts have concentrated on charting the suitability of nanocellulose for various novel applications. The chemical functionalization of cellulose is currently regarded as a significant step for both enhancing nanocellulose fabrication and increasing its value as a product by virtue of its adjustable surface properties. This thesis reports on the surface functionalization of cellulosic fibres by means of two new chemical pre-treatments based on periodate oxidation and sequential chlorite oxidation or reductive amination for use in the fabrication of nanocelluloses. The properties of the resulting nanocelluloses were characterized and their applicability to novel film structures was investigated. Both nanoporous thin films for composite membranes and self-standing barrier films were manufactured and studied for their suitability in water purification and packaging applications, respectively. The oxidation of cellulose to 2,3-dicarboxylic acid cellulose (DCC) significantly enhanced the nanofibril production as only 1-4 passes through the homogenizer were required for disintegration of the fibres down to nano-scale. The fabricated DCC-nanofibrils had both high optical transmittance and viscosity comparable to that of TEMPO-oxidized cellulose nanofibrils. DCC-nanofibrils with a carboxyl content of 1.75 mmol/g showed a potential for functioning as a nanoporous thin-film membrane layer in ultrafiltration tests. The second pre-treatment introduced an acid-free fabrication of amphiphilic cellulose nanocrystals (CNCs) with uniform width and length into nanocellulose production for the first time. Reaction conditions of periodate oxidation were presumed to be one of the key factors to impact the formation of either CNCs or cellulose nanofibrils. The butylamino-functionalized CNCs were used to fabricate barrier films that showed good mechanical strength and high resistance to permeation by oxygen even at elevated relative humidity. / Tiivistelmä Yksi metsäteollisuuden viimeisimmistä tuoteinnovaatiosta on nanoselluloosa, jolle on esitetty lukuisia uusia sovellusmahdollisuuksia sekä potentiaalia toimia korvaavana raaka-aineena öljypohjaisille tuotteille sen erinomaisten materiaaliominaisuuksien sekä globaalin saatavuuden ja uusiutuvuuden takia. Nanoselluloosan teollista hyödyntämistä on kuitenkin hidastanut kustannustehokkaiden valmistusmenetelmien puuttuminen. Samanaikaisesti on tehty laaja-alaista tutkimustyötä nanoselluloosan soveltuvuudesta uusiin käyttökohteisiin. Selluloosan kemiallista funktionalisointia pidetään tällä hetkellä yhtenä lupaavimpana menetelmänä tehostamaan sekä nanoselluloosan valmistusta että tuomaan lisäarvoa nanokuiduille, joiden pintaominaisuuksia voidaan muokata. Tässä työssä tutkittiin selluloosakuitujen funktionalisointia perjodaattihapetukseen sekä kloriittihapetukseen tai pelkistävään aminointiin perustuen ja nanoselluloosan valmistusta esikäsitellystä selluloosasta. Työssä tutkittiin erityisesti valmistettujen nanoselluloosien ominaisuuksia ja selvitettiin niiden soveltuvuutta uudentyyppisiin filmirakenteisiin. Filmirakenteita muokkaamalla tehtiin nanohuokoisia komposiittimembraaneita vedenpuhdistukseen sekä barrier-filmejä pakkausmateriaaleihin. Selluloosan hapetus 2,3-dikarboksyylihapposelluloosaksi tehosti nanoselluloosan valmistusta huomattavasti ja kuidut saatiin hajotettua 1-4 läpäisyllä homogenisaattorissa. Valmistetut DCC-nanofibrillit olivat optisesti läpinäkyviä sekä niiden viskositeetti oli yhtä korkea kuin aiemmin raportoiduilla TEMPO-hapetettuilla nanofibrilleillä. Ultrasuodatuskokeissa DCC-nanofibrilleistä pystyttiin muodostamaan nanohuokoinen kerros membraaninpinnalle, jota on mahdollista käyttää vedenpuhdistuksessa. Pelkistävällä aminointiesikäsittelyllä selluloosakuiduista onnistuttiin ensimmäistä kertaa valmistamaan kooltaan yhdenmukaisia amfifiilisiä selluloosananokiteitä ilman yleisesti käytettyä happohydrolyysiä. Siten työssä nanoselluloosien valmistukseen käytetyn perjodaattihapetuksen havaittiin soveltuvan sekä selluloosananokiteiden että selluloosananofibrillien valmistukseen. Butyyliamino-funktionalisoiduista selluloosananokiteistä valmistetut barrier-filmit olivat mekaanisesti vahvoja ja ne ehkäisivät hapenläpäisyä jopa korkeassa ilmankosteudessa.

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