Industrial utilization of polymeric gas separation membranes is predicted to increase significantly over the next 20 years. This growth will be driven by application of membrane based separations to increasingly aggressive feed streams. In this work, the performance of defect-free Matrimid asymmetric hollow fiber membranes in the presence of high pressure carbon dioxide and trace levels of toluene and n-heptane in the feed stream are studied. Specifically, this work shows a significant decrease in the carbon dioxide plasticization pressure and the carbon dioxide permeance prior to plasticization as a result of accelerated physical aging at ambient temperature. Interestingly, sub-Tg thermal annealing at 220 oC reverses the effects of physical aging by increasing the plasticization pressure and the carbon dioxide permeance prior to plasticization for a typical polyimide commonly used in membranes. The performance of Matrimid asymmetric hollow fiber membranes in feed streams contaminated with up to 1200 ppm toluene and 2000 ppm n-heptane is investigated. In the presence of both feed stream contaminants, the productivity and efficiency of the membrane are observed to significantly decrease in this work. These decreases in performance are shown to be the result of antiplasticization, and a free volume based model is developed to correlate the effect of feed stream contamination on membrane performance

This work was performed as a preliminary transdermal drug delivery (TDD) study to investigate the diffusion characteristics and effects of skin surfactants in vitro of four active ingredients on a poly(dimethyl siloxane) polycarbonate copolymer membrane. A Franz-type diffusion cell and various receptor solutions were used. The adhesive used was comprised of a polyisobutylene-based pressure sensitive adhesive manufactured by Adhesives Research Inc. High performance liquid chromatography was used to analyze the diffusion characteristics of these systems. In addition, the effects of two skin surfactants (sodium lauryl sulfate and dimethyl sulfoxide) on the adhesive were also investigated. Results from peel testing and thermal analysis showed that the peel strength, glass transition, and softening temperature of the adhesive was greatly reduced with the addition of the surfactants. / Master of Engineering

Bending wood dates back to antiquity in the form of baskets from willow branches and when boats were no longer made of hollowed out logs. Fresh growth willow twigs are readily bent into practically any shape; however, when wood has been separated from the tree and dried it is more rigid, difficult to bend, and breakable. Steamed wood is less rigid since adding moisture and heat to wood results in plasticization. Steaming at atmospheric pressure is the common technique for wood bending where diffusion prevails as the predominant mechanism governing moisture movement. Applications using conventional atmospheric steaming are time consuming and can result in failed bends. While other wood plasticization methods exist, Vacuum Steam Technology offers a promising method that utilizes pressure differentials to accelerate the addition of steam to wood due to water vapor bulk flow and subsequently an accelerated temperature rise and moisture addition. The objectives of this work were: (1) determine whether cycles of vacuum and steaming could significantly improve the plastic-deformable state relative to the classic process of atmospheric steaming given equivalent treatment times when beginning with low moisture content (<10%) maple, and (2) compare the work required to bend to form between Vacuum Steam Technology treated maple and atmospheric-steamed maple when beginning with low moisture content (<10%) specimens. A procedure for Vacuum Steam Technology to enable rapid plasticization of maple specimens from a kiln-dried state was developed. Kiln dried maple specimens were either treated according to the Vacuum Steam Technology procedure or were atmospherically steamed for a time equivalent to the Vacuum Steam Technology treatment and then bent into a 180° semi-circular form. Vacuum Steam Technology treated specimens had 0 failed bends whereas the atmospheric steamed specimens resulted in 39% failed bends. Vacuum Steam Technology treated specimens resulted in 17% less work to bend. The results clearly indicate that Vacuum Steam Technology is a superior technique for attaining a plastic deformable state prior to bending when beginning with low moisture content maple. Additional results included time to temperature, rate of moisture content change, final moisture contents, specific gravity influence. / Master of Science

Le polylactide (PLA) est un polymère à la fois biodégradable et biosourcé focalisant l'attention des chercheurs pour le remplacement des plastiques conventionnels. A la température ambiante, le PLA est fragile et nécessite d’être modifié par plastification physique afin d’augmenter sa ductilité, mais dans le même temps sa rigidité chute fortement. Une alternative à cette plastification physique est la plastification par extrusion réactive. L’extrusion réactive du PLA avec l’acrylate de poly(éthylène glycol) (acrylPEG) donne lieu à un PLA plastifié nommé pPLA. Cette thèse a pour objectifs l’identification de la structure du pPLA et l’étude de son évolution lors de transformations thermomécaniques d’étirage et de recyclage. La structure du pPLA a été analysée par une approche multi-échelles et multidisciplinaire. L’acrylPEG polymérisant et formant des inclusions, est partiellement greffé au PLA et partiellement libre. De plus, les réactions conduisent à une légère réticulation de la matrice. La présence de plastifiant conduit à un bon équilibre entre rigidité et ductilité. Les mécanismes de déformation du pPLA sous étirage ont montré que les mécanismes d’orientation moléculaire sont prépondérants par à l’endommagement, qui lui prédomine dans le PLA. L’analyse du recyclage thermomécanique du pPLA a mis en évidence une dégradation du matériau dépendant du type de procédé utilisé. L’utilisation de la compression à chaud est le procédé le plus défavorable, conduisant à une dégradation plus importante du pPLA par rapport au PLA. Ces travaux ont permis de développer des méthodologies de caractérisation permettant une meilleure identification structurale des biopolymères / Polylactide (PLA), a biodegradable and bio-based polymer, raised researchers’ attention to replace conventional plastics. At room temperature, PLA is brittle and requires physical plasticization that increases its ductility but at the same time drastically decreases its stiffness. As an alternative, plasticization by reactive extrusion was recently developed. The reactive extrusion of PLA with acrylated poly(ethylene glycol) (acrylPEG) as plasticizer yields a plasticized PLA named pPLA. This thesis aims at identifying the structure of this pPLA and studying its evolution engendered by thermomechanical transformations as drawing and recycling. First, pPLA’s structural features are analyzed by a multi-scale and multi-disciplinary approach. pPLA is characterized by partially grafted and partially free inclusions of the polymerized plasticizer and a slightly crosslinked PLA matrix. These plasticizer inclusions lead to a material with a good stiffness-ductility balance. Second, the deformation mechanisms of pPLA upon drawing indicate that chain orientation mechanisms are predominant compared to damage, the latter dominating deformation in PLA. Third, the thermomechanical recycling of pPLA shows that degradation is dependent on the type of processing step. Compression-molding is detrimental to pPLA inducing after recycling a higher degradation compared to PLA. This thesis releases new characterization methodologies enabling a better identification of biopolymer structural features

This research project investigated physical aging and carbon dioxide plasticization behavior of glassy polymer films. Recent studies have shown that thin glassy polymer films undergo physical aging more rapidly than thick films. This suggests that thickness may also play a role in the plasticization and conditioning responses of thin glassy films in the presence of highly-sorbing penetrants such as CO₂. The effect of film thickness on CO₂ permeation and sorption was studied extensively through carefully defined and controlled methods that provide a basis for future study of plasticization behavior. Thin films are found to be more sensitive than thick films to CO₂ exposure, undergoing more extensive and rapid plasticization at any pressure. The response of glassy polymers films to CO₂ is not only dependent on thickness, but also on aging time, CO₂ pressure, exposure time, and prior history. Thin films experiencing constant CO₂ exposure for longer periods of time exhibit an initial large increase in CO₂ permeability, which eventually reaches a maximum, followed by a significant decrease in permeability for the duration of the experiment. Thick films, in contrast, do not seem to exhibit this trend for the range of conditions explored. For a series of different polymers, the extent of plasticization response tracks with CO₂ solubility. There is little data available for gas sorption in thin glassy polymer films. In this work, a novel method involving spectroscopic ellipsometry is used to obtain simultaneously the film thickness and CO₂ sorption capacity for thin glassy polymer films. This allows a more comprehensive look at CO₂ permeability, sorption, and diffusivity as a function of both CO₂ pressure and exposure time. Like the gas permeation data, these experiments suggest that thin film sorption behavior is substantially different than that of thick film counterparts. Dynamic ellipsometry experiments show that refractive index minima, fractional free volume maxima, and CO₂ diffusivity maxima correlate well with observed CO₂ permeability maxima observed for thin Matrimid® films. These experiments demonstrate that plasticization and physical aging are competing processes. Aging, however, dominates over long time scales. Over time, CO₂ diffusivity is most affected by these competing effects, and the evolution of CO₂ diffusivity is shown to be the main contributing factor to changes in CO₂ permeability at constant pressure. / text

Natural gas is among the most dominant resources to provide energy supplies and Saudi Arabia ranks among the top 5 producers worldwide. However, prior to use of methane, natural gas has to be treated to remove other feed gas components, such as H2O, CO2, H2S, N2 and C2+ hydrocarbons. Most NG fields in KSA contain about 10 mol% carbon dioxide that has to be reduced to less than 2 mol% for pipeline delivery. The conventional unit operations for natural gas separations, that is, molecular sieves, amine absorption, cryogenic distillation, and turbo expansion exhibit some disadvantages in terms of economics, operational flexibility or system footprint. One of the most attractive alternative is membrane technology in either standalone- or hybrid system configuration. Currently, the only two membrane materials used in industrial natural gas applications are cellulose acetate and polyimide, which have moderate permeability and fairly low selectivity when tested under realistic industrial conditions. The goal for future research is to develop unique polymeric membranes, which can at least partially replace conventional gas processing in future natural gas projects. This will support global economics and specifically the economy of Saudi Arabia. Newly developed polymeric materials must meet certain criteria to be used on a commercial scale. These criteria include: (i) high permeability and selectivity, (ii) processability into thin films, (iii) mechanical and thermal stability, and (iv) chemical stability against feed gas components. This project focused on the removal of carbon dioxide from natural gas by developing and characterizing functionalized aromatic polyimide membrane materials that exhibit very high selectivity under aggressive mixed-gas conditions. 6FDA-DAR demonstrated a mixed-gas CO2/CH4 selectivity of 78 at a CO2 partial pressure of 10 bar with no pronounced indication of plasticization. Combining hydroxyl- and carboxyl groups in a miscible polyimide blend led to mixed-gas CO2/CH4 selectivity of 100 with no aging and no plasticization effects. This burgeoning membrane material has very high potential in large-scale natural gas separations with the best overall performance of any type developed to date.

The influence of plasticization and other formulation factors on the properties of hot-melt extruded dosage forms for the controlled release of water-soluble active compounds was investigated. Citric acid monohydrate was demonstrated to function as a solid-state plasticizer in hot-melt extruded Eudragit® RS PO tablets and in cast films when concentrations below the compatibility limit were employed. Melting of the organic acid and solubilization in the polymer during extrusion were necessary to observe the plasticizing effect. The release rate of diltiazem hydrochloride, used as a high-melting, water-soluble model drug, from melt extruded Eudragit® RS PO matrix tablets increased and became independent of the original drug particle size in the presence of citric acid monohydrate. Thermal analysis of physical mixtures demonstrated that citric acid promoted drug melting during extrusion by interaction and melting point depression. Diltiazem hydrochloride remained amorphous in the final dosage form, and leaching of citric acid monohydrate enhanced drug diffusion by increasing the matrix porosity. Delayed-release matrix pellets with particle sizes below one mm were prepared by hot-melt extrusion, and the influence of the matrix forming polymer and the type and level of plasticizer on the processibility and release properties was investigated. Pellets complied with the USP requirement for delayed release articles to release less than 10% drug at pH 1.2 after 2 hours when plasticized Eudragit® S100 was used as the release-controlling material. High levels of efficient plasticizers had to be employed to decrease the polymeric melt viscosity, increase the process yield and enable extrusion at moderate temperatures to avoid instabilities during processing and storage. The aqueous solubility of the plasticizer further impacted the drug release rate in acid. A novel application of hot-melt extrusion for the preparation of monolithic matrices comprising enteric coated particles was studied. The influence of the mechanical strength of the multiparticulates, pellet loading and nature of the hydrophilic carrier material on the preservation of the delayed-release properties after extrusion was investigated. Soft particles coated with brittle films remained intact when low-melting carriers that did not solubilize the enteric film during extrusion were used, and the dissolution profile was stable over one year. / text

Compared to the conventional amine adsorption process to separate CO₂ from natural gas, the membrane separation technology has exhibited advantages in easy operation and lower capital cost. However, the high CO₂ partial pressure in natural gas can plasticize the membranes, which can lead to the loss of CH₄ and low CO₂/CH₄ separation efficiency. Crosslinking of polymer membranes have been proven effective to increase the CO₂ induced plasticization resistance by controlling the degree of swelling and segmental chain mobility in the polymer. This thesis focuses on extending the success of crosslinking to more productive asymmetric hollow fibers. In this work, the productivity of asymmetric hollow fibers was optimized by reducing the effective selective skin layer thickness. Thermal crosslinking and catalyst assisted crosslinking were performed on the defect-free thin skin hollow fibers to stabilize the fibers against plasticization. The natural gas separation performance of hollow fibers was evaluated by feeding CO₂/CH₄ gas mixture with high CO₂ content and pressure.

Both novel membrane materials with better separation characteristics and a better fundamental understanding of membrane transport stability are needed to improve the competitiveness of commercial membrane separations. In this work, the effect of a novel moiety, hexafluoroalcohol, on the gas transport properties of an aromatic polyimide membrane are evaluated. The hexafluoroalcohol group increases the membrane’s fractional free volume, which increases the membrane’s permeability to all gases. Additionally, the HFA-containing polyimide shows resistance to plasticization by carbon dioxide. However, ideal selectivity for several gas pairs is unchanged by the inclusion of hexafluoroalcohol and the increase in the polymer’s fractional free volume. This lack of selectivity loss with increasing free volume is attributed to hydrogen bonding between the hexafluoroalcohol and imide groups, which reduces chain mobility. The ethanol dehydration characteristics of a so-called “TR” polymer are also evaluated in this work. TR polymers are heterocyclic, aromatic polymers synthesized by a solid-state, high temperature condensation from ortho-functional polyimides. Pervaporation studies on a representative TR polymer film demonstrate that the material has separation properties that exceed those of a commercial ethanol dehydration membrane. The transport properties of the TR film, combined with high thermal and chemical stability characteristic of these materials, make TR polymers promising materials for high-temperature, high-water content ethanol dehydration. Finally, the physical aging and plasticization of cellulose triacetate, the dominant natural gas purification membrane, is presented. Although this material has been used industrially for over 30 years, the physical aging and plasticization of the material, particularly in sub-micron films, has never been studied. Although cellulose triacetate does show physical aging behavior, as observed by permeability decreases over time, cellulose triacetate thin films do not show accelerated aging. Furthermore, the plasticization of thin cellulose triacetate films is reduced, rather than increased as seen in other polymers. The unusual transport stability of thin cellulose triacetate films may be due to their complex, semi-crystalline morphology, which, due to the thermal instability of the material, may not be thermally controlled. / text

Orientadores: Fernanda Paula Collares, Theo Guenter Kieckbusch / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-08T12:08:34Z (GMT). No. of bitstreams: 1 Takeiti_CristinaYoshie_D.pdf: 20201216 bytes, checksum: c1aa9903ccb493780afa2e5957c1db81 (MD5) Previous issue date: 2007 / Resumo: Maltodextrinas são oligossacarídeos solúveis em água, provenientes da hidrólise de amidos. As condições da hidrólise permitem definir a distribuição de massa molecular das maltodextrinas e, conseqüentemente, suas características funcionais podem ser ajustadas para aplicações distintas e específicas. Estes ingredientes são empregados em formulações de pós alimentícios prontos para o consumo e, portanto, o conhecimento de atributos que afetam sua reconstituição em água é determinante para o desenvolvimento desses produtos. Maltodextrinas comerciais com diferentes graus de dextrose-equivalente (DE) e provenientes de três fábricas nacionais distintas foram avaliadas quanto à: morfologia das partículas, teor de umidade, massa molecular, diâmetro médio, densidade aparente e real, porosidade, tempo de molhamento, tempo de dissolução, grau de cristalinidade, isotermas de sorção de umidade e temperatura de transição vítrea (Tg). Os pós comerciais apresentaram características morfológicas distintas, o que influenciou o seu desempenho quanto às propriedades de reconstituição em água. Os produtos que apresentaram características intermediárias de reconstituição foram submetidos a um processo de aglomeração por jato a vapor em mini-instantaneizador para melhorar suas qualidades tecnológicas. As condições de operação foram otimizadas por metodologia de superfície de resposta. O produto aglomerado de maltodextrina com DE igual a 10 apresentou o melhor rendimento e excelentes propriedades instantâneas, enquanto que, a maltodextrina com maior grau de DE, isto é, com menor Tg apresentou o menor rendimento de processo e um produto com piores características de reconstituição. A tendência geral indica que a morfologia e características instantâneas dos aglomerados obtidos foram influenciadas pela temperatura de transição vítrea. Um estudo complementar realizado em leito fluidizado com paredes de acrílico, utilizando soluções de maltodextrina como ligante entre partículas sólidas inertes, avaliou as condições de solidificação das pontes vítreas. A relação umidade vs temperatura obtida confirmou que o processo de aglomeração é influenciado pela massa molecular das amostras e, conseqüentemente, por suas Tgs. Esses parâmetros devem ser considerados no dimensionamento e/ou condições de operação de aglomeradores / Abstract: Maltodextrins are water soluble oligossacharides produced by starch hydrolysis. Their functional characteristics depend on their molecular mass distributions which can be taylormade for specific applications through the control of the process conditions during hydrolysis. Maltodextrin are widely used as ingredient in instant food powder mixes and the knowledge of their reconstitution attributes would assist the development of new formulations. Commercial maltodextrins produced by three different Brazilian manufacturers with dextrose-equivalent (DE) degrees ranging from 5 to 20 were evaluated with respect to morphology, moisture content, molecular mass distribution, average particle diameter, bulk and true densities, void fraction, wetting and dissolution times, crystallinity degree, equilibrium isotherms and glass transition temperature (Tg). The maltodextrin powder showed distinct morphological features, which influenced their water reconstitution abilities. The products with moderate instant properties were submitted to a steam jet agglomeration process in a pilot plant instantiser in order to improve their technological qualities. The operational conditions were optimized by surface response methodology. The general trend indicated that the agglomerates morphology as well as their instant properties are influenced by the glass transition temperature. The DE10 maltodextrin agglomerates showed the best process yield and superior instant properties. The agglomerates of maltodextrin with the highest DE, which has the lowest Tg , showed the lowest yield and poor reconstitution properties. A complementary study, conducted in an Plexiglassÿ fluidized bed equipment using maltodextrin solutions as ligand, evaluated the formation of vitreous bridges between inert particles. The moisture content/temperature relations obtained supported the assumption that the agglomeration process is influenced by the molecular mass of the samples and, consequently, by their Tgs. These parameters should be considered in the design and /or operational conditions of agglomerators / Doutorado / Tecnologia de Alimentos / Doutor em Tecnologia de Alimentos