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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

Investigation of the effects of curing and casting methods on the physicochemical properties of polymeric coating systems

Li, Yingjian 01 December 2016 (has links)
This study is to evaluate the effect of curing and casting methods on the physicochemical properties of polymeric coating systems. Aqueous-dispersion-based and organic-solvent-based Kollicoat® SR30D (poly(vinyl acetate)) and Kollicoat® MAE100P (poly(methacrylic acid-ethyl acrylate)) free films or film-coated pellets were used to evaluate the physicochemical properties resulting from different solvents and different curing treatments. Diffusion coefficients of water in organic-solvent-based films were lower than those in aqueous-dispersion-based films. Increases in curing temperature and curing time decreased the diffusion coefficient. Regardless of preparation method, the tensile strengths of films increased with an increase in curing temperature and curing time. Changes in elongation percentage of the films were dependent on the polymer and curing. The tensile strengths of aqueous-dispersion-based SR30D films are lower compared to those of organic-solvent-based SR30D films. However, the “core-shell” structure is preserved in the aqueous-dispersion-based MAE100P film and formed a rigid frame, which greatly increased the mechanical properties of the films. Therefore, the tensile strength of aqueous-dispersion-based MAE100P films is greater than in the case of organic-solvent-based films. In swelling studies, water uptake and weight loss for all of the films increased with an increase in incubation time. The water uptake and weight loss of SR30D films cast from water were higher than those of organic-solvent-based films. However, contradictory results were observed for MAE100P films due to the core-shell structure in the aqueous-dispersion-based MAE100P films. An increase in curing time and temperature increased the Tg of SR30D films. Curing treatments led to a second glass transition temperature for MAE100P films, which may result from microphase separation. Curing decreased acetaminophen release from pellets coated with an aqueous-dispersion-based SR30D film. Curing effects are also dependent on the coating formulation and coating parameters. The drug release rate from organic-solvent-based film-coated pellets was slower in comparison to pellets coated with aqueous-dispersion-based films. Acetaminophen release in 0.1 N HCl from aqueous-dispersion-based MAE100P coated pellets was reduced after the curing treatment. Curing has no effect on drug release for acetaminophen-containing pellets coated with organic-solvent-based SR30D or MAE100P films. The ionization of surface carboxylic-acid groups on MAE100P polymer particles alters the properties of polymer films by increasing ionic aggregates and solubilizing the polymer chains. Increased ionic aggregates improve the mechanical properties of films. However, solubilizing polymer chains will change the film formation mechanism from a dispersion-based film to a solution-based film. Therefore, tensile strength was decreased with an increase in ionization degree. The drug release rates were continuously increased when the degree of ionization of surface acid groups increased. Overall, curing and casting methods have significant effects on the physicochemical properties of SR30D and MAE100P films and on the drug release behavior from film-coated, drug-loaded pellets. The core-shell structure in aqueous-dispersion-based MAE100P films also greatly changed the properties of this film or coat.
2

Aqueous film-coating with the ultra-coater (hybrid coater)

Kwok, Swee Har Teresa January 2004 (has links)
Hydroxypropylmethylcellulose (HPMC), which is available in different degrees of substitution and viscosity designations, is one of the most commonly used cellulosic polymers in aqueous film coating. It is relatively easy to process due to its non-tacky nature and has been known to produce smooth and clear films. For aqueous film coating, it is cost effective to use a coating formulation containing a high concentration of polymer without affecting the viscosity or spray rate and compromising on the quality of the film coat. Hence, it is ideal to use a polymer of low viscosity grade. The rheological properties of HPMC with various viscosity grades were determined. It was found that HPMC Methocel E3 had the lowest viscosity and was the least affected by the increase in polymer concentration. Additives can modify the film properties, including the glass transition temperature of the coating polymer. Glass transition temperature influences the viscosity of the coating solution and the mechanical properties, adhesion and permeability of the film coat. Various concentrations of different additives were incorporated in HPMC formulations to study the effect on these properties. Some long-chain fatty acids were included in the study to investigate if their hydrophobic carbon chains could retard moisture permeation of HPMC films. It was observed that HPMC films containing water-soluble additives produce films with clarity similar to those without additives, whereas those with hydrophobic additives tend to be patchy or hazy in appearance. A vinyl pyrrolidone / vinyl acetate copolymer (S630) was investigated for its influence on HPMC films, comparing the results with a commonly used plasticizer, polyethylene glycol (PEG) and another copolymer, polyvinyl alcohol (PVA). Intrinsic properties of the solutions, such as viscosity and glass transition temperature, were evaluated. / The effect of S630 on the film properties, such as physical appearance, surface roughness, moisture permeation and mechanical properties, as well as its ability to promote better adhesion of the film coat to the core surface, were compared. S630 was found to be effective both as a film-former and plasticizer, reducing the glass transition temperature and viscosity, but enhancing the tensile strength, elongation and work of failure of the cast film. The water vapour permeability was slightly increased but not to the same extent as with polyethylene glycol PEG). A 10% concentration of this copolymer increased the adhesive strength and toughness of the HPMC film coat. Aqueous film coating was carried out in the ultra-coater, using HPMC coating formulations containing 8% w/w of solids, without or with 10% concentration (based on dry weight of total solids) of the additives, PEG, polyvinyl alcohol (PVA) and S630, for coating the tablets. Capsule-shaped lactose tablet cores of specific surface area, hardness, weight, friability and disintegration time were used to study the process variables. Process variables, including air flow rate, temperature and humidity, coating application rate or pump flow rate, atomising air pressure and speed of the rotating disk, were investigated in order to obtain the optimum operating conditions for these solutions. It was found that the process parameters were similar for all the coating formulations containing 8% solid. The additives used in the coating formulations had little influence on the coating process. The ultra-coater was an effective unit for the aqueous film coating of tablets with a batch size of not less than 5 kg.
3

The Study and Fabrication of Optical Coating on Cr4+:YAG Crystal Fiber

Lin, Yu-Hsien 09 July 2004 (has links)
In the last years, intensive research on new tunable solid state laser materials has been carried out. For the spectral range from 1300 to 1600 nm the Cr4+ ion seems to be the most promising laser-ion. In order to meet the the demand of broad-band devices, we employed the Cr4+ doped YAG crystal fibers with high optical quality thin films design and coating (high index material TiO2, low index material SiO2) to achieve the development of high efficiency crystal fiber lasers. In this thesis, crystal fiber was used as the laser gain medium, and coated with optical thin films at both end faces (input face 900-1100 nm AR and 1300-1600 nm HR; output face 1300-1600 nm HR) as the laser cavity to reduce the loss and promote laser efficiency. During the experiment, we tried to optimize the coating conditions to acquire high density, stable index and low absorption coefficient thin films. With different thin film thickness and stacking designs, the electric field distribution was designed to be away from the laser interface and high index region to increase the laser-induced damage threshold and lifetime for high power pumping. In addition, CaO and Cr2O3 were deposited on Cr4+:YAG source rods before the laser-heated-pedestal growth to increase CaO and Cr2O3 doping concentration for higher fluorescence efficiency and signal saturation power.
4

Tatamento e recobrimento de sementes de soja com polímeros líquido e em pó / Soybean seed treatment and coating with liquid and powdered polymer

Avelar, Suemar Alexandre Gonçalves 18 March 2009 (has links)
Made available in DSpace on 2014-08-20T13:44:44Z (GMT). No. of bitstreams: 1 dissertacao_suemar_goncalves_avelar.pdf: 341956 bytes, checksum: 84385fd5f8e00822859f151c0afe5a06 (MD5) Previous issue date: 2009-03-18 / Seed coating is a strong technology for soybean seeds, bringing great advantages to the farmers, allowing the application of polymers in an appropriate and necessary way to cover the seed. The objective of this research was to evaluate the efficiency of seed coating and the quality of soybean seeds treated with fungicide, insecticide, micronutrients and polymers, during six months of storage. Soybean seeds cultivar CD 209 were submitted to the following treatments: control, fungicide Fludioxonil + Metalaxyl - M (Maxim XL® - 100 mL.100 kg-1 seeds), insecticide Thiametoxan (Cruiser 350 FS® - 200 mL.100 kg-1 seeds), micronutrient ComoFix® (165 mL.100 kg-1 seeds - 24,75 mL Mo and 2,475 mL Co) and the mixture fungicide + insecticide + micronutrient. The same treatments were repeated using the liquid polymer Sepiret 9241 B Green (400 mL.100 kg-1 seed) and also powder polymer Sepiret Flo Branco (0,5 kg.100 kg-1 seeds) + colorant Corasem blue (50 mL.100 kg-1 seeds). Coating efficiency and physical and physiological seed quality in laboratory and seedling performance in the field were evaluated. It was concluded that: the use of polymer in seed coating presents seeds with good appearance, coloration, distribution and adherence of the products to the seed surface; uniformity of product distribution during seed treatment varies with the interaction between product and type of polymer used. Coating with liquid polymer is more efficient in soybean seeds. The use of polymers alters the hectolitre volumetric weight not affecting the physiologic quality. The powder polymer presents adverse latent effects after the storage of the seeds. The polymer should not be used separately in the treatment of seeds. / O recobrimento de sementes é uma tecnologia que vêm se firmando cada vez mais, pois traz grandes vantagens ao agricultor, permitindo a aplicação de polímeros de forma adequada e precisa à semente. O objetivo deste trabalho foi avaliar a eficiência do recobrimento e a qualidade de sementes de soja tratadas com fungicida, inseticida, micronutrientes e polímeros líquido e em pó, durante seis meses de armazenamento. Sementes de soja do cultivar CD 209 foram submetidas aos seguintes tratamentos: testemunha, fungicida Fludioxonil + Metalaxyl M (Maxim XL® - 100 mL.100 kg-1 sementes), inseticida Thiametoxan (Cruiser 350 FS® - 200 mL.100 kg-1 sementes), micronutriente ComoFix® (165 mL.100 kg-1 sementes 24,75 mL Mo e 2,475 mL Co) e a mistura fungicida + inseticida + micronutriente. Os mesmos tratamentos foram repetidos utilizando o polímero líquido Sepiret 9241 B Green (400 mL.100 kg-1 semente) e também o polímero em pó Sepiret Flo Branco (0,5 kg.100 kg-1 sementes) + o corante Corasem azul (50 mL.100 kg-1 sementes). Foram avaliadas a eficiência do recobrimento, qualidade física e fisiológica das sementes em laboratório e o desempenho de plântulas em campo. Concluiu-se que: o uso de polímeros no recobrimento apresentou sementes com boa aparência, coloração, distribuição e aderência dos produtos á superfície das mesmas. A uniformidade de distribuição dos produtos no tratamento de sementes varia com a interação entre produto e tipo de polímero utilizado. O polímero líquido é mais eficiente no recobrimento de sementes de soja. O uso de polímeros altera o peso hectolítrico das sementes de soja, não afetando a qualidade fisiológica. O polímero em pó apresenta efeito latente adverso após o armazenamento das sementes. Os polímeros não devem ser utilizados isoladamente no tratamento de sementes.
5

Qualidade fisiológica de sementes de soja tratadas com fungicida e recobertas com polímeros / Physiological quality of soybeans seeds treated with fungicide and coating with polymers

Benatto Junior, João Carlos 06 May 2008 (has links)
Made available in DSpace on 2014-08-20T13:44:41Z (GMT). No. of bitstreams: 1 dissertacao_joao_carlos_benatto_jr.pdf: 93588 bytes, checksum: 357cf23c63a8a8f690a9bf4dd7d3511a (MD5) Previous issue date: 2008-05-06 / The use of polymers in soybean seeds has been accomplished with the purpose of incorporating products like insecticides, fungicides, growing substances, minor fertilizers and so on, in order to improve the visual aspect of the seed, to promote smaller operator's intoxication risk and to provide a better seeds' acting and seedlings after sowing. The main objective of this work was to evaluate the recovered seeds' effects in soybeans seed quality lots of high and low germination of the cv. AG 7000. The seed's film coating was accomplished with two commercial marks of polymers, LABORSAN ® , and LANXESS ® , in doses of 2 and 3,5 ml for each kg with and without mixture of the fungicide Carbendazim + Thiram (firewalk ® ). The seeds' quality evalutions, were measured by the germination test, germination in sand and accelerated aging. The use of polymers in soybean seeds provides seeds with good appearance and coloration and can be applied to differentiate the seed from the commercial grain. The fungicide and the polymers do not affect the physiological quality of soybean seed. The results of the polymers and fungicide were superior in the test of accelerated aging, showing higher germination in relation to the check treatment. / O uso de polímeros em sementes de soja vem sendo realizado com a finalidade de incorporar produtos fitossanitários, melhorar o aspecto visual da semente, promover menor risco de intoxicação do operador e proporcionar um melhor desempenho de sementes e plântulas após a sua semeadura. O objetivo principal deste trabalho foi avaliar o efeito do recobrimento na qualidade de semente de soja de alta e baixa germinação da cv. AG 7000. O revestimento foi realizado com duas marcas comerciais de polímeros, LABORSAN ® , e LANXESS ® , nas doses de 2 e 3,5 mL para cada kg de semente com e sem mistura do fungicida Carbendazim + Thiram (firewalk ® ). As avaliações da qualidade das sementes foram realizadas por meio do teste de germinação, germinação em substrato de areia e envelhecimento acelerado. O uso de polímeros na semente de soja proporciona sementes com boa aparência e coloração, podendo ser aplicado para diferenciar a semente do grão comercial. O fungicida e o polímero não prejudicam a qualidade fisiológica da semente de soja. Os resultados do polímero e fungicida foram superiores no teste de envelhecimento acelerado, apresentando maior percentual de germinação em relação à testemunha.
6

ANTIMICROBIAL EFFICACY OF EDIBLE SOY PROTEIN ISOLATE FILMS AND COATINGS INCORPORATED WITH HOP ETHANOL EXTRACT AND THE INFLUENCE ON SHELF-LIFE AND SENSORY ATTRIBUTES OF BOLOGNA

Skudlarek, Jamie R. G. 01 January 2012 (has links)
There is demand for improved security of refrigerated ready-to-eat meats. Antimicrobial edible films and coatings could function as an added barrier against post-processing contamination. Hops and hop extracts are known for their antimicrobial efficacy which is attributed to key antimicrobial components including humulones, lupulones, xanthohumol and various terpenoids. Yet, hop ethanol extract has not been studied as an antimicrobial to incorporate into edible protein films and/or coatings. The overall objective of this research was to evaluate hop ethanol extract as an antimicrobial agent incorporated into edible soy protein isolate (SPI) films and coatings, and the influence on the shelf-life and sensory attributes of bologna. Hop ethanol extract was examined for minimum inhibitory concentration before the extract was incorporated into a 6% SPI solution at 0, 10, and 20% levels to determine antimicrobial efficacy as a cast film and simulated coating via zone of inhibition against Listeria monocytogenes strains ATCC 4644, UKADL and ATCC 49594. The results showed that hop ethanol extract alone was inhibitory of all three strains. Moreover, the hop ethanol extract, when incorporated at 10 and 20% (v/v) into edible soy protein isolate (SPI) films and simulated coatings, exhibited antimicrobial action against all three L. monocytogenes strains. Key antimicrobial components, as mentioned above, were identified in the hop ethanol extract via mass spectrometry. The SPI with 10% incorporated hop ethanol extract (SPI+10%hop) antimicrobial coating was applied to bologna, prepared in lab without L. monocytogenes inhibitors, where it exhibited a significant (P ≤ 0.05) bacteriostatic effect against strain ATCC 4644. The SPI+10% hop coating was then applied to a commercial bologna to examine effects on shelf-life and sensory attributes. Significant differences (P ≤ 0.05) were found in instrumental red and yellow colors, however not in sensory color. There was no significant difference (P > 0.05) found in measured lipid oxidation between the bologna with no coating, SPI coating or SPI+10%hop coating. The incorporation of hop did exhibit a slightly bitter taste. Overall, these findings indicate that the SPI+10%hop antimicrobial coating functioned as an inhibitor of L. monocytogenes while producing minimal effects on shelf-life and sensory attributes of bologna.
7

Performance da aplicação de polímero no tratamento de sementes de amendoim /

Furlani, Ana Caroline Ferreira Athayde. January 2009 (has links)
Resumo: Devido à importância da cultura do amendoim na região de Jaboticabal e à necessidade de incremento em sua tecnologia de produção, o objetivo do presente trabalho foi avaliar a possibilidade de utilizar a técnica de peliculização em sementes dessa cultura. Foram realizados três ensaios: a) em laboratório, sobre o efeito do tratamento na germinação e vigor de sementes de amendoim, b) em casa de vegetação, sobre a eficiência do tratamento na germinação de sementes em solo infestado com Rhizoctonia solani e c) ensaio em campo, sobre a influência do tratamento na produção da cultura. Foram utilizados dois lotes de sementes de amendoim, da cultivar Runner IAC 886, de alto e baixo vigor. As sementes receberam os seguintes tratamentos: testemunha, polímero Laborsan® (2,0 mL.kg-1 sementes), fungicida Fludioxonil (Maxin XL) - (1,5 mL.kg-1 sementes) revestido com o polímero Laborsan® (2,0 mL.kg-1 sementes) e fungicida Fludioxonil (Maxin XL) - (1,5 mL.kg-1 sementes). O nível de vigor das sementes teve efeito em todas as avaliações realizadas. O polímero utilizado neste trabalho não afetou o potencial fisiológico das sementes de amendoim, nem a eficiência do fungicida testado, mostrando-se uma técnica promissora, porém, deve ser utilizado somente em conjunto com fungicidas por não controlar patógenos de solo. / Abstract: Due to the importance of the peanut culture in Jaboticabal region and to the necessity of increase its production technology, the objective of the present work was to evaluate the possibility of to utilize the film-coating technique in this culture seeds. It was realized three assays: a) in laboratory relating to the effect of the treatment on peanut seeds germination and vigor, b) in greenhouse relating to seeds germination in infested soil with Rhizoctonia solani and c) in the field assay relating to the influence of treatment on culture production. It was utilized two peanut seed lots of Runner IAC 886 cultivar with high and low vigor. Seeds received the following treatments: control, Laborsan® film-coating (2,0 mL.kg-1 seeds), fungicide Fludioxonil (Maxin XL) - (1,5 mL.kg-1 seeds) recovered with the Laborsan® film-coating (2,0 mL.kg-1 seeds) and fungicide Fludioxonil (Maxin XL) - (1,5 mL.kg-1 seeds). Seeds vigor level had effect in all evaluations. The film-coating used in this work did not affect peanut seeds physiological potential and either the fungicide efficiency, showing a promising technique, however, it must had utilized only with fungicide because it does not control soil pathogens. / Orientadora: Rita de Cassia Panizzi / Coorientador: Rubens Sader / Banca: Margarida Fumiko Ito / Banca: Nilvanira Donizete Tebaldi / Banca: Margarete Camargo / Banca: Adriana Zanin Kronka / Doutor
8

Performance da aplicação de polímero no tratamento de sementes de amendoim

Furlani, Ana Caroline Ferreira Athayde [UNESP] 16 February 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:33:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-16Bitstream added on 2014-06-13T19:23:47Z : No. of bitstreams: 1 furlani_acfa_dr_jabo.pdf: 199667 bytes, checksum: 7b60a60b8477ecba5b3dfc86cfb914ac (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Devido à importância da cultura do amendoim na região de Jaboticabal e à necessidade de incremento em sua tecnologia de produção, o objetivo do presente trabalho foi avaliar a possibilidade de utilizar a técnica de peliculização em sementes dessa cultura. Foram realizados três ensaios: a) em laboratório, sobre o efeito do tratamento na germinação e vigor de sementes de amendoim, b) em casa de vegetação, sobre a eficiência do tratamento na germinação de sementes em solo infestado com Rhizoctonia solani e c) ensaio em campo, sobre a influência do tratamento na produção da cultura. Foram utilizados dois lotes de sementes de amendoim, da cultivar Runner IAC 886, de alto e baixo vigor. As sementes receberam os seguintes tratamentos: testemunha, polímero Laborsan® (2,0 mL.kg-1 sementes), fungicida Fludioxonil (Maxin XL) – (1,5 mL.kg-1 sementes) revestido com o polímero Laborsan® (2,0 mL.kg-1 sementes) e fungicida Fludioxonil (Maxin XL) – (1,5 mL.kg-1 sementes). O nível de vigor das sementes teve efeito em todas as avaliações realizadas. O polímero utilizado neste trabalho não afetou o potencial fisiológico das sementes de amendoim, nem a eficiência do fungicida testado, mostrando-se uma técnica promissora, porém, deve ser utilizado somente em conjunto com fungicidas por não controlar patógenos de solo. / Due to the importance of the peanut culture in Jaboticabal region and to the necessity of increase its production technology, the objective of the present work was to evaluate the possibility of to utilize the film-coating technique in this culture seeds. It was realized three assays: a) in laboratory relating to the effect of the treatment on peanut seeds germination and vigor, b) in greenhouse relating to seeds germination in infested soil with Rhizoctonia solani and c) in the field assay relating to the influence of treatment on culture production. It was utilized two peanut seed lots of Runner IAC 886 cultivar with high and low vigor. Seeds received the following treatments: control, Laborsan® film-coating (2,0 mL.kg-1 seeds), fungicide Fludioxonil (Maxin XL) – (1,5 mL.kg-1 seeds) recovered with the Laborsan® film-coating (2,0 mL.kg-1 seeds) and fungicide Fludioxonil (Maxin XL) – (1,5 mL.kg-1 seeds). Seeds vigor level had effect in all evaluations. The film-coating used in this work did not affect peanut seeds physiological potential and either the fungicide efficiency, showing a promising technique, however, it must had utilized only with fungicide because it does not control soil pathogens.
9

Polymeric controlled release film coatings / Films d'enrobage polymérique pour des formes galéniques solides à libération contrôlée

Fahier, Julie 25 October 2016 (has links)
Les mini-granules enrobées offrent un grand potentiel pour la libération contrôlée de médicament par voie orale. Cependant, les mécanismes de libération impliqués ne sont pas toujours élucidés et compris. Ainsi, l’impact de certains paramètres de formulation peut être surprenant. Par exemple, il a été démontré dans ce travail :- La libération du propranolol HCl à partir de mini-granules enrobées avec du Kollicoat SR est plus lente si les mini-granules sont composées de noyaux de sucre comparé à des noyaux de cellulose microcristalline (CMC).Généralement, la tendance inverse est observée, car les noyaux de sucre ont une activité osmotique attirant plus rapidement l’eau à l’intérieur du système et entrainant ainsi, une dissolution et diffusion de la substance active. Ce résultat inattendu est dû à une association de 2 phénomènes : (i) l’effet plastifiant dû au sucre sur le film de Kollicoat SR et (ii) la diminution de la solubilité de cette SA dans le milieu de dissolution en présence de sucre dissous.De plus, le Kollicoat SR 30 D [dispersion aqueuse de poly(vinyl pyrrolidone)] offre des possibilités intéressantes de formulation par sa haute flexibilité et ses propriétés mécaniques stables. En revanche, les mini-granules composées de noyaux de sucre ont tendance à gonfler de par le cumul de l’activité osmotique du noyau et de la SA jusqu’à l’apparition de « cracks », révélés par des images obtenues par micro tomographie à rayons X.- Lorsqu’on augmente la quantité en propranolol HCl dans le système, la cinétique de libération est augmentée, particulièrement avec les mini-granules composées de noyaux de CMC.L’opposé est souvent constaté car accroitre la quantité de SA nécessite un plus grand apport en eau afin de pouvoir tout dissoudre. Les mini-granules à base de CMC présentent probablement des « cracks » malgré un faible gonflement du système, et sont accentués par l’augmentation de la concentration en propranolol HCl.En conclusion, des nouvelles connaissances sur les mécanismes de libération à partir de mini-granules enrobées avec du Kollicoat SR ont été apportées et l’importance du type de SA et la nature du noyau composant le système ont été élucidées.- Dans une deuxième partie, des mini-granules enrobées avec un mélange de polymère (Aquacoat ECD et Eudragit NM 30 D) ont été formulées dans le but de libérer la diprophylline, SA modèle, par diffusion à travers le film de polymère et de pouvoir modéliser sa cinétique à partir de modèles mathématiques. / Polymer coated pellets offer a great potential for control drug delivery system. Nevertheless, the underlying drug release mechanisms can be complex and are not fully understood. Thus, the impact of formulation parameters can be surprising. For example, it has been demonstrated during this thesis that:- The release of propranolol HCl was slower from sugar-based pellets coated with Kollicoat SR compared to microcrystalline cellulose (MCC)-based pellets.Generally, the opposite was observed because the sugar cores are osmotically active attracting more and more water into the system leading to a fast dissolution and diffusion of the drug, especially with high water-soluble drug. This unexpected result is due to a combination of two phenomena: (i) The plasticizing effect of sugar for the film coating and (ii) Decrease in drug solubility in the release medium due to the presence of co-dissolved sugar.In addition, Kollicoat SR 30 D [an aqueous dispersion of poly(vinyl acetate) also containing small amounts of poly(vinyl pyrrolidone) and sodium lauryl sulfate] is a very interesting polymer owing to its high flexibility and stable mechanical properties. However, sugar-based pellets tend to swell by the osmotic pressure created by the high water-soluble API and the sugar until crack formation, clearly visible on the images obtained by X-ray micro tomography.- Propranolol HCl release in phosphate buffer pH 7.4 increases by increasing the drug loading into the system, especially from MCC-based pellets.The opposite was often observed since the amount of water within the drug reservoir might not be sufficient to dissolve all drug. MCC-based pellets likely presented also cracks despite a low swelling of the system, accentuated by the increase of propranolol HCl concentration.To conclude, new insights on the underlying drug release mechanisms from Kollicoat SR coated pellets were provided. The importance of the type of drug and the nature of starter cores were elucidated.- In the second part, diprophylline loaded pellets coated with a polymer blend composed of Aquacoat ECD and Eudragit NM were prepared in order to control the drug release only by diffusion through the intact polymeric film and to predict the drug kinetics using mathematical models.
10

Growth of Carbon Nanotubes on Model and Supported Catalysts

Medhekar, Vinay S 20 August 2004 (has links)
"Catalytic growth of Carbon Nanotubes (CNT) provides important advantages of controlling their diameters and possibly chirality. Our work involved growing CNT on model and supported catalyst by catalytic decomposition of carbon source such as benzene, methane and propylene. On supported catalyst, iron nitrate was deposited on alumina and reduced to form metallic iron clusters. These were reacted at 700 - 950 C under varying benzene concentrations. Multi Walled CNT (MWNT) grew below 800 C and Single Wall CNT (SWNT) are observed at 850 C and above as confirmed by TEM and Raman. Model catalysts were studied by producing CNT from ferrocene which acted as the carbon and catalyst source on Silica/Si (100). Large yield of MWNT was observed at 900 C. MWNT grew perpendicular to the model support as seen by SEM. In another model catalyst study, iron salt clusters were deposited on silica/Si (100) by spin coating, controlling their diameters by solution concentration and speed of spinning. Agglomeration of clusters at high temperatures produces only MWNT on silica/Si (100). Cluster agglomeration can be reduced with strong support metal interaction such as with alumina. We deposited alumina on silica/Si (100) by atomic layer deposition, with conformal coatings on surface and low relative roughness. Alumina film was stable under reaction temperatures of 900 C. Cluster deposition on alumina by spin coating was difficult because of different surface acidity compared to silica. Clusters on alumina did not agglomerate at high reaction temperatures. We report effect of parameters such as the temperature of reaction, conditions of pretreatment such as reduction and oxidation of catalyst precursor, type of precursor, type of carbon source, and type of support material on growth of CNT. The role of spin coating in controlling the diameter of salt clusters deposited is discussed. We also report deposition of alumina on top of silica/Si (100) by atomic layer deposition and the effect of deposition and calcination temperatures on the alumina film integrity."

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