Controleld Morphology and Mechanical Characterisation of Electrospun Cellulose Acetate Fibre Webs

The purpose was to interpret the varying morphology of electrospun cellulose acetate (CA) fibres produced from single and binary solvent systems based on solubility parameters to identify processing conditions for the production of defect-free CA fibrous webs by electrospinning. The Hildebrand solubility parameter () and the radius of the sphere in the Hansen space () of acetone, acetic acid, water, N,N-dimethylacetamide (DMAc), methanol, and chloroform were examined and discussed for the electrospinning of CA. The Hildebrand solubility parameter () of acetone and DMAc were found to be within an appropriate range for the dissolution of CA. The suitability of the binary solvent system of acetone: DMAc (2 : 1) for the continuous electrospinning of defect-free CA fibres was confirmed. Electrospun webs exhibited improved tensile strength and modulus after heat and alkali treatment (deacetylation) of the as-spun material, and no major fibre morphological degradation occurred during the deacetylation process

Correlating Interlayer Spacing and Separation Capability of Graphene Oxide Membranes in Organic Solvents.

Membranes synthesized by stacking two-dimensional graphene oxide (GO) hold great promise for applications in organic solvent nanofiltration. However, the performance of a layer-stacked GO membrane in organic solvent nanofiltration can be significantly affected by its swelling and interlayer spacing, which have not been systematically characterized. In this study, the interlayer spacing of the layer-stacked GO membrane in different organic solvents was experimentally characterized by liquid-phase ellipsometry. To understand the swelling mechanism, the solubility parameters of GO were experimentally determined and used to mathematically predict the Hansen solubility distance between GO and solvents, which is found to be a good predictor for GO swelling and interlayer spacing. Solvents with a small solubility distance (e.g., dimethylformamide, N-methyl-2-pyrrolidone) tend to cause significant GO swelling, resulting in an interlayer spacing of up to 2.7 nm. Solvents with a solubility distance larger than 9.5 (e.g., ethanol, acetone, hexane, and toluene) only cause minor swelling and are thus able to maintain an interlayer spacing of around 1 nm. Correspondingly, GO membranes in solvents with a large solubility distance exhibit good separation performance, for example, rejection of more than 90% of the small organic dye molecules (e.g., rhodamine B and methylene blue) in ethanol and acetone. Additionally, solvents with a large solubility distance result in a high slip velocity in GO channels and thus high solvent flux through the GO membrane. In summary, the GO membrane performs better in solvents that are unlike GO, i.e., solvents with large solubility distance

Production of syndiotactic polystyrene powder for part manufacturing through SLS

Selective laser sintering (SLS) is a well-established additive manufacturing (AM) process. While AM originally found its use as rapid prototyping technique, it is nowadays more and more considered for the production of actual end-use parts. A widely acknowledged hindrance in the evolution of this technology is the limited range of materials available for processing with SLS, making the application window rather small. Introducing new materials with the correct morphology and thermal requirements for SLS could broaden this window and give rise to new products. This research aims at identifying such promising materials, considering the relevant requirements for selecting and processing a new material. Considered foremost within this manuscript is the processability of syndiotactic polystyrene from pellet form into spherical particles of 50-90 μm without significantly changing their properties. Regarding processing methods, the focus of this work is on solution based techniques (single phase precipitation, emulsion precipitation) instead of more conventional mechanical processing methods (ball milling) as these are believed to be more accessible and more suitable as a precursor step for a wide range of processing technique

Molecular Characteristics of Kraft-AQ Pulping Lignin Fractionated by Sequential Organic Solvent Extraction

Kraft-AQ pulping lignin was sequentially fractionated by organic solvent extractions and the molecular properties of each fraction were characterized by chemical degradation, GPC, UV, FT-IR, 13C-NMR and thermal analysis. The average molecular weight and polydispersity of each lignin fraction increased with its hydrogen-bonding capacity (Hildebrand solubility parameter). In addition, the ratio of the non-condensed guaiacyl/syringyl units and the content of β-O-4 linkages increased with the increment of the lignin fractions extracted successively with hexane, diethylether, methylene chloride, methanol, and dioxane. Furthermore, the presence of the condensation reaction products was contributed to the higher thermal stability of the larger molecules

Comparing Physical Properties and Industrial Applications of Some Lactic Acid Esters

Bakalářská práce se zabývá charakterizací esterů kyseliny mléčné na základě jejich fyzikálně-chemických vlastností. Vybrány byly methyl, ethyl, 2-ethylhexyl, n-propyl, isopropyl ester kyseliny mléčné. Tyto estery jsou biologicky rozložitelné, a proto jsou v této bakalářské práci uvažovány jako možná náhrada nebezpečnějších a toxičtějších rozpouštědel v průmyslové výrobě. Z tenze par určené pomocí izoteniskopu byly stanoveny parametry Antoineové rovnice a Hildebrandův parametr rozpustnosti.The bachelor thesis deals with characterization of lactic acid esters on the basis of their physicochemical properties. Methyl, ethyl, 2-ethylhexyl, n-propyl, isopropyl lactate were selected. These esters are biodegradable and they are therefore considered as replacement for more toxic and dangerous solvents for industrial use. Antoine equation and Hildebrand solubility parameter was calculated from vapour pressure measured by isoteniscope.

Understanding the Thermodynamic Behavior of Nanoparticles to Tailor Polymer Nancomposite Structure

The work presented in this dissertation is an attempt to understand the entropic and enthalpic forces that govern the dispersion and dissolution of nanoparticles in solutions and in thin polymer films with the end-goal of producing highly tailored products. In the first part, neutron reflectivity was used to study the impact of nanoparticle presence on the surface segregation of deuterated polystyrene (dPS) in a polystyrene matrix. The impact of the presence of cylinders (carbon nanotubes), sheets (graphene), and spheres (polystyrene soft nanoparticles) on the surface segregation process and ultimate structure were examined. Experimental data indicate that the presence of the nanoparticles slows the dPS diffusion in all cases, and the soft nanoparticles, which contained branching and more chain ends than the dPS linear polymer matrix, are entropically driven to the air surface, resulting in a decreases of excess dPS at the surface and a decrease in free energy of the system. Graphene had the opposite effect, segregating to the silicon surface due to a higher surface energy and enhancing the dPS segregation to the air surface. The next part focuses on developing a protocol using static light scattering and refractometry to quantitatively determine the solubility behavior of boron containing nanoparticles. With scattering, the second virial coefficient is obtained and used to calculate the solute-solvent interaction parameter, [chi], which quantifies the mixing behavior. UV-Vis spectroscopy and physical observations were also used to describe the systems. The solubility behavior of carboranes, boron nitride nanotubes and sheets, and single walled carbon nanotubes (SWNTs) were quantified. In all cases there is good agreement between the measured data and [chi]. Suitable solvents were also predicted based on the calculation of the Hildebrand solubility parameter, [delta]. Use of [delta] to predict solubility shows good agreement for the smaller particles, but is more suspect for the nanotubes and sheets due to additional entropic factors. Finally, two purification techniques for SWNTs, acid purification and purification via centrifugation in surfactant, were examined. Experimental evidence indicates that centrifugation leads to the isolation of more pristine tubes, appropriate for applications that require increased electrical conductivity

Evaluation of the contribution to hydration of nonelectrolytes from the hydrophobic effect

A new method was suggested for estimating the hydrophobic effect of contributions to the Gibbs energies and enthalpies of hydration of hydrocarbons, inorganic gases and rare gases. In accordance with this method the hydrophobic effect contribution to the Gibbs energy was evaluated from the difference between the hydration Gibbs energy of a solute and the non hydrophobic contribution. To estimate the latter value, the known dependence connecting the Gibbs energies of solvation of a solute in a number of aprotic solvents to the Hildebrand solubility parameter for these solvents was used. The non hydrophobic contribution to the Gibbs energy of hydration was calculated for various solutes from such dependences extended to water as solvent. The Hildebrand solubility parameter for water used in the calculation was corrected for the effect of association through hydrogen bonding. This correction was made by subtraction of the water self-association enthalpy from the enthalpy of vaporization of water. The evaluated Gibbs energies of the hydrophobic effect are positive for saturated hydrocarbons, inorganic gases and rare gases and linearly depend on the solute molecular refraction. The hydrophobic contribution to the hydration enthalpies of the solutes was calculated in the same manner as was made to calculate the hydrophobic contribution to Gibbs energies of hydration. Enthalpies of the hydrophobic effect for the solutes under study are negative. © 1995 Plenum Publishing Corporation

Uso de los parámetros de solubilidad de Hansen como mejora del modelo cinético de la reacción catalizada de síntesis de BTBE

Treballs Finals de Màster d'Enginyeria Química, Facultat de Química, Universitat de Barcelona. Curs: 2019-2020. Tutor: Carles Fité PiquerThe prediction of reaction rates of the BTBE synthesis reaction is enhanced by including the reaction medium effect in the kinetic model, as demonstrated in a previous study based on experimental kinetic data. The Hildebrand solubility parameter was used to predict such interaction. The aim of the present work is to check if the use of the Hansen solubility parameters presents an advantage over Hildebrand solubility parameters in the kinetic modelling of the studied reaction, because it is based on a more accurate description of intra- and intermolecular forces. Several estimation methods will be considered to find Hansen solubility parameters. The method which provides the best accurate results, will be used to find Hansen solubility parameters of BTBE. Different tests are carried out to check if Hansen solubility parameters depend significantly on temperature. At this point, the kinetic equation obtained from the previous work and other kinetic equations will be tested to find the best results that describe the kinetics of the BTBE synthesi

Prediction of solid–binder affinity in dry and aqueous systems: Work of adhesion approach vs. ideal tensile strength approach

Wet granulation process requiresthe addition of a coating agentor binder, typicallycomposed of surfactants such as hydroxypropyl-methylcellulose (HPMC), water and a small amount offiller such as stearic acid (SA). In dry granulation however, the coating agent is added to the system in the form offine solid particles. In both cases, a successful granulation requires good affinity between host and guest particles. In this study, we compare two approaches to predict the binder–substrate affinity in dry and in aqueous media, one based on the work of adhesion and the other based on the ideal tensile strength (Rowe, 1988). The novelties of this paper are four folds. First, the equations used in both approaches are generalized and rewritten as a function of the Hildebrand solubility parameter δ.δ is obtained from molecular simulations or predicted from HSPiP group contribution method. Secondly, a correlation between δ and the experimental surface tension γ is established for cellulose de-rivative (such as HPMC and ethyl cellulose). Thirdly, the concept of ideal tensile strength, originally formalized by Gardon (1967) for binary systems, is extended to ternary systems and applied for granulation in aqueous media. Fourthly, the approaches are tested for various systems and compared to experimental observations. For dry bi-nary systems, predicted adhesive and cohesive properties agree with literature experimental observations, but the work of adhesion approach performs better than the ideal tensilestrength approach. Both approaches predict thatHPMCisa good binderfor microcrystallinecellulose (MCC).The results alsoindicate that polyethyleneglycol 400(PEG400)has a good affinity with HPMC and stearic acid. For ternary aqueous systems, the results fully agree with the observations of Laboulfie et al.(2013)