Veneer-based structural wood composites are typically manufactured using phenol-formaldehyde resols (PF) that are formulated with wheat flour extender and organic filler. Considering that this technology is several decades old, it is surprising to learn that many aspects of the formulation have not been the subject of detailed analysis and scientific publication. The effort described here is part of a university/industry research cooperation with a focus on how the organic fillers impact the properties of the formulated adhesives and adhesive bond performance. The fillers studied in this work are derived from walnut shell (Juglans regia), alder bark (Alnus rubra), and corn cob (furfural production) residue. Alder bark and walnut shell exhibited chemical compositions that are typical for lignocellulosic materials, whereas corn cob residue was distinctly different owing to the high pressure steam digestion used in its preparation. Also, all fillers had low surface energies with dominant dispersive effects. Surface energy of corn cob residue was a little higher than alder bark and walnut shell, which were very similar. All fillers reduced PF surface tension with effects greatest in alder bark and walnut shell. Surface tension reductions roughly correlated to the chemical compositions of the fillers, and probably resulted from the release of surface active compounds extracted from the fillers in the alkaline PF medium. It was shown that viscoelastic network structures formed within the adhesive formulations as a function of shear history, filler type, and filler particle size. Relative to alder bark and walnut shell, the unique behavior of corn cob residue was discussed with respect to chemical composition. Alder bark and walnut shell exhibited similar effects with a decrease of adhesive activation energy. However, corn cob reside caused much higher adhesive activation energy. Alder bark exhibited significant particle size effects on fracture energy and bondline thickness, but no clear size effects on penetration. Regarding corn cob residue and walnut shell, particle size effects on fracture energy were statistically significant, but magnitude of the difference was rather small. Classified corn cob residue fillers all resulted in a similar bondline thickness (statistically no difference) that was different walnut shell. / Ph. D.

This dissertation investigates the behavior of the Escherichia Coli mechanosensitive (MS) channel MscL, when incorporated within a droplet interface bilayer (DIB). The activity of MscL channels in an artificial DIB system is demonstrated for the first time in this document. The DIB represents a building block whose repetition can form the basis to a new class of smart materials. The corresponding stimuli-responsive properties can be controlled by the type of biomolecule incorporated into the lipid bilayer, which is in the heart of this material. In the past decade, many research groups have proven the capability of the DIB to host a wide collection of natural and engineered functional biomolecules. However, very little is known about the mechano-electrical transduction capabilities of the DIB. The research present herein specifically seeks to achieve three direct goals: 1) exploring the capabilities of the DIB to serve as a platform for mechano-electrical transduction through the incorporation of bacterial MscL channels, 2) understanding the physics of mechano-electrical transduction in the DIB through the development of theoretical models, and 3) using the developed science to regulate the response of the DIB to a mechanical stimulus. MscL channels, widely known as osmolyte release valves and fundamental elements of the bacterial cytoplasmic membrane, react to increased tension in the membrane. In the event of hypo-osmotic shocks, several channels residing in the membrane of a small cell can generate a massive permeability response to quickly release ions and small molecules, saving bacteria from lysis. Biophysically, MscL is well studied and characterized primarily through the prominent patch clamp technique. Reliable structural models explaining MscL's gating mechanism are proposed based on its homolog's crystal structure modeling, which lead to extensive experimentation. Under an applied tension of ~10 mN/m, the closed channel which consists of a tight bundle of transmembrane helices, transforms into a ring of greatly tilted helices forming an ~8 A water-filled conductive pore. It has also been established that the hydrophobicity of the tight gate, positioned at the intersection of the inner TM1 domains, determines the activation threshold of the channel. Correspondingly, it was found that by decreasing the hydrophobicity of the gate, the tension threshold could be lowered. This property of MscL made possible the design of various controllable valves, primarily for drug delivery purposes. For all the aforementioned properties and based on its fundamental role of translating cell membrane excessive tensions into electrophysiological activities, MscL makes a great fit as a mechanoelectrical transducer in DIBs. The approach presented in this document consists of increasing the tension in the lipid bilayer interface through the application of a dynamic mechanical stimulus. Therefore, a novel and simple experimental apparatus is assembled on an inverted microscope, consisting of two micropipettes (filled with PEG-DMA hydrogel) containing Ag/AgCl wires, a cylindrical oil reservoir glued on top of a thin acrylic sheet, and a piezoelectric oscillator actuator. By using this technique, dynamic tension can be applied by oscillating one droplet, producing deformation of both droplets and area changes of the DIB interface. The tension in the artificial membrane will cause the MS channels to gate, resulting in an increase in the conductance levels of the membrane. The increase in bilayer tension is found to be equal to the sum of increase in tensions in both contributing monolayers. Tension increase in the monolayers occurs due to an increase in surface area of the constant volume aqueous droplets supporting the bilayer. The results show that MS channels are able to gate under an applied dynamic tension. Interestingly, this work has demonstrated that both electrical potential and surface tension need to be controlled to initiate mechanoelectric coupling, a property previously not known for ion channels of this type. Gating events occur consistently at the peak compression, where the tension in the bilayer is maximal. In addition, the experiments show that no activity occurred at low amplitude oscillations (< 62.5um). These two findings basically present an initial proof that gating is occurring and is due to the mechanical excitation, not just a random artifact. The role of the applied potential is also highlighted in this study, where the results show that no gating happens at potentials lower that 80 mV. The third important observation is that the frequency of oscillation has an important impact of the gating probability, where no gating is seen at frequencies higher than 1 Hz or lower than 0.1 Hz. Each of the previous observations is addressed separately in this research. It was found that the range of frequencies to which MscL would respond to in a DIB could be widened by using asymmetrical sinusoidal signals to stimulate the droplets. By increasing the relaxation time and shorting the compression time, a change in the monolayer's surface area is achieved, thus higher tension increase in the bilayer. It was also found that a high membrane potential assists in the opening of MscL as the droplets are stimulated. This is due to the sensitivity of MscL to the polarity of the signal. By using the right polarity the channel could be regulated to become more susceptible to opening, even at tensions lower than the threshold. Finally, it was demonstrated, for the first time, that MscL would gate in asymmetric bilayers without the need to apply a high external potential. Asymmetric bilayers, which are usually composed from different lipids in each leaflet, generate an asymmetric potential at the membrane. This asymmetric potential is proven to be enough to cause MscL to gate in DIBs upon stimulation. / Ph. D.

On the basis of the present data it would seem that there is no marked relationship between the surface tension and the degree of polymerization of nitrocellulose solutions of normal butyl acetate as determined by the Du Nouy method. It should be noted that no great precision is present in the recorded data. A slight change in surface tension due to a difference in the degree of polymerization could easily be more than offset by errors in measurement. The solutions become much more viscous with increased concentration. This limited the range over which the surface tension could be measured with any degree of accuracy. For with highly viscous solutions the ring would be pulled slowly from the surface making it extremely difficult to determine the exact force required for the break. A second effect was that with increasing concentration a film of the solution adhered across the ring. The data indicates that there is no great change in the surface tension with varying concentration within the range studied. / M.S.

It is well known that surface tension of a liquid has a decisive role in flow dynamics and the eventual equilibrium state, especially in confined flows under low gravity conditions and also in free surface flows. One such instance of a combination of these two cases where surface tension plays an important role is in the microgravity environment of a spacecraft propellant tank. In this specific case both propellant acquisition and residual propellant estimation are critical to the mission objectives particularly in the end-of-life phase. While there have been a few studies pertaining to the equilibrium state in given geometric configurations, the transient flow leading to final state from an initial arbitrary distribution of propellant is rarely described. The present study is aimed at analysing the dynamic behaviour of the liquids under reduced gravity through numerical simulation and also addresses the specific case of propellant flow transient in a cone-in-a-sphere type of tank configuration proposed by Lal and Raghunandan which is likely to result in both improved acquisition and life time estimation of spacecraft. While addressing this specific problem, the present work aims to study the transient nature of such surface tension driven flows in a general form as applicable to other similar problems also. Volume of Fluid (VOF) method for multiphase model in ANSYS FLUENT was adapted with suitable changes for generating numerical solutions to this problem. Simulations were run for three different cone angles of 17o, 21o & 28o with a flat liquid surface for full scale models to measure the rise height and time of rise. Two scaled models of ½ and 1/10th of the original dimensions with the same liquid configuration of the 28o cone angle case were simulated to see if the time scales involved would come down for experimental feasibility. A third simulation of the 1/10th scale model was run with the liquid spread in the tank to imitate the general conditions found in the propellant tank in microgravity. To understand the behaviour of liquids in the microgravity state to changing physical parameters, a set of simulations was run using liquid phases as water and hydrazine with different physical parameters of temperature and surface tension. The theory put forward by Lal and Raghunandan was found to stand firm. In the case of the cone angle of 28o it was observed that in the final equilibrium state the liquid collected towards the apex of the cone with the larger volume fraction of liquid accumulating inside the cone. An addition of a cylindrical section at the bottom of the cone seems to help although not uniformly for all case. The equilibrium settling times for all the three cone angle cases were in the order of 300 to 600 seconds for simulations on a spherical tank of diameter two metres which was close to the actual tank dimension used on spacecraft. Scaled down simulations of 1/10th and ½ the tank geometry with both flat liquid surfaces and spread out liquid volumes showed that the smaller models had equilibrium settling times which were considerably lower (in the order of tens of seconds) than the full scale models. Although smaller, these time scales are larger than the maximum time scales available in drop tower tests which provide a maximum free fall time of around 9 to 10 seconds. Validation of the proposed configuration by flying an aircraft in a parabolic flight path is a possibility that could be explored for the scaled down models since the zero-g duration for these flights is on an average between 15-20 seconds.

The scope of this thesis is micromanipulation in liquid media. This scientific field aims at understanding the relevant phenomena existing during the manipulation in a liquid of microcomponents having a size between $1,micrometer$ and a few millimeters. This work focuses on the study of surface tension forces in immersed media, because they have favorable scaling effect. The main idea is to use gas bubbles as actuation mean in a liquid, and requires to study the mechanical properties of these bubbles. The originality of the approach is the combination of two effects: surface tension and gas compressibility. <p><p>The first step was the study of an efficient mean to generate a single bubble of predefined size. After a detailed review, it appeared that volume controlled bubble generation was a promising method. We have then developed a model to predict the size of a bubble, and emphasized the possible existence of a growing instability. An analytic dimensionless study allowed to define a criterion to predict the existence of this instability.<p><p>The second step aimed at the mechanical characterization in quasi static equilibrium of a gas bubble caught between two solids. The purpose is to predict the force generated by the bubble, together with its stiffness. The model implemented allowed to infer interesting properties, notably a high compliance whose value is controllable by fluidic parameters. This compliance property being very important during micromanipulation, a demonstrator making use of gas bubbles has been designed and manufactured. It consists in a compliant microtable actuated by three bubbles. This work opens the way to new actuation or sensing means, using the transduction between fluidic and mechanic energy operated by a capillary bridge.<p>/<p>Cette thèse a pour contexte la micromanipulation en milieu liquide. Cette thématique scientifique vise à comprendre les phénomènes qui interviennent lors de la manipulation dans un liquide de microcomposants, dont la taille peut varier entre $1,micrometer$ et quelques millimètres. Les travaux de cette thèse se sont focalisés sur l'étude des forces de tension de surface en milieu immergé, car elles bénéficient d'effets d'échelle favorables. L'idée poursuivie est d'utiliser des bulles de gaz comme un moyen d'actionnement dans les milieux liquides, et nécessite d'étudier les propriétés mécaniques de ces bulles. L'originalité de l'approche repose sur la combinaison de deux effets :la tension de surface et la compressibilité du gaz.<p><p>La première étape a été l'étude d'un moyen efficace pour générer une unique bulle de gaz de taille voulue. Après une analyse exhaustive, il est apparu que la génération de bulle par le contrôle en volume était une méthode prometteuse. Nous avons alors développé un modèle permettant de prédire la taille d'une bulle, et mis en évidence la possible existence d'une instabilité de la croissance de ces bulles. Une étude analytique adimensionnelle nous a permis de définir un critère pour prédire l'existence ou non de cette instabilité. <p><p>La seconde étape a porté sur la caractérisation mécanique en régime quasi statique d'une bulle de gaz en contact avec deux solides. Le but étant de prédire la force générée par une bulle de gaz sur les solides ainsi que sa raideur. Le modèle implémenté a permis de déduire des propriétés intéressantes des bulles de gaz, notamment une grande compliance dont la valeur peut être contrôlée par des paramètres fluidiques. Cette propriété de compliance étant très recherchée en micromanipulation, un démonstrateur exploitant les bulles de gaz a été conçu. Il s'agit d'une microtable compliante actionnée par trois bulles. Ces travaux ouvrent la voie vers de nouveaux modes d'actionnement ou de capteur utilisant la transduction entre une énergie fluidique et mécanique opérée par un ménisque capillaire. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

No description available.

M. Tech. (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Presently, the current membrane technologies used in oil/water separation are inefficient with poor controllability and stability during oil/water separation. The has led to the current problem of membrane fouling and degradation during oil/water separation. Several approaches have been used to modify or design a better wettable surface with limited success since the current problem of membrane fouling is persisting. It is, therefore, necessary for scientists, engineers, and researchers to come up with a new membrane technology that will be more efficient with stable wettability and controllability during oil/water separation. Membranes are made up of nanoparticles on their surface, which are both random in nature. Furthermore, the collection of membrane particles to form mesh membranes are made of pores with further ransom spatial distribution. Thus, it was necessary to use the tools of stochastic processes to theoretically characterize these parameters. These parameters affect both internal and external factors as well as characteristics of random membrane particle and pores on wettability like surface tension and surface energy were established in the current project. Design and production of the membrane material according to established relationships was by both low and high-pressure spay jet coating in a controlled laboratory environment, and microscopic characterization performed using SEM. TEM, EDS, statistical analysis, and Image J particle analyzer. The spread, orientation, morphology, spatial distribution, inter-separation distances, surface roughness, surface smoothness, contact angles, surface density of the particle, mean size of the coated nanoparticle on the membrane surface after different coating rounds were analyzed so as to establish conditions for optimal wettability. The testing of produced membranes under the application of external and internal factors was done. A centrifugal pump was used to pump contaminated oil and water mixture through the membrane under a steady flow rate of 10 L/s with a gauge pressure of 180 kPa at room temperature conditions. The membrane materials from different coating rounds were tested for their abilities to produce pure collected water or oil particles in the collected water. The separated water was analyzed using oil and grease analysis US EPA method 1664B with the SPE-DEX 1000 oil and grease system. As revealed theoretically and validated experimentally, it was found that the random natures of nanoparticle size, the spatial distribution of membrane channels, and their morphology have impacts on surface energy-driven separability of oil and water mixture. It was also observed that the scattering of nanoparticles on the membrane surface during coating lowered surface energy, which enhanced oil/water separation. It was also revealed that there is an optimal nanoparticle size, scattering, morphology, and spatial distribution of membrane channels that offer better separation of water from oil. From the microscopy analysis, different microstructures were revealed for glass, ceramics, and sediment during LP and HP coating. The microstructure characterization showed different surface densities of nanoparticles, mean particle sizes, surface roughness or smoothness, and nanoparticles inter-separation distances. It was also revealed that the materials, which were more stable and efficient with more controlled wettability were glass, sediment, and ceramic HP 3rd rounds of coating. Clusters were observed on the membrane surface during HP and LP coating rounds with more clusters observed in LP coating when compared with HP coating. These clusters increased surface energy, which negatively affected oil/water separation. It was concluded that to improved the wettability surface. membrane clusters must be minimized during coating rounds. This thesis contributed new knowledge to existing body knowledge of membrane technology used in oil/water separation in a number of ways by: (1) Designing a new membrane surface with a more controlled, efficient, and stable wettability process during oil/water separation. (2) Applying the logic of surface energy-driven separability, which has not been previously used extensively to study membrane wettability. (3) Establishing a model for the optimal membrane pore sizes that offer optimal membrane wettability during oil/water separation. (4) Establishing a model for optimal nanoparticle coating that offers optimal membrane wettability during oil /water separation. (5) A great attempt was made in characterizing nanoparticle surface densities, spread, particle coating, and nanoparticles intensity on a wettable membrane surface.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The purpose of this study is to construct and test a surface tension driven water pump. The surface tension driven water pump is a passive water pump which uses a similar mechanism to that of trees to pump water. This study was conducted at the Department of Mechanical and Mechatronic Engineering at the University of Stellenbosch. For the study an extensive literature survey was done encompassing aspects such as water properties, surface tension (basic principles, capillary forces, temperature and contaminant effects, wettability), bubble formation (nucleation theory and tensile strength of water) and, finally water and mineral transport in trees (plant structures and mechanisms, limiting factors, misconceptions and organic substance transport). Previous work by botanists who demonstrate the transpiration mechanism needed for water transport in trees was also considered. The study further required the development of a theoretical thermal-hydraulic model to simulate the pumping performance for the surface tension driven water pump. The developed water pump was also experimentally tested with particular focus on design improvement, pumping performance, pump behaviour, potential pumping head as well as water collection capability. The experimental data was statistically analysed by multi-linear regression. Both the experimental data and statically generated predictions were compared to the theoretical thermal-hydraulic model. The results show that a working surface tension driven pump was constructed. Evaporation rates of up to 400 mL/hr.m2 were obtained, with pumping head heights reaching up to 1.8 m and a maximum pump functional lifespan of 13 days. The results further suggest that there is a good correlation between the various statistical fits and the experimental data. The developed theoretical thermal-hydraulic model was also found to be in good agreement with the experimental results. A sensitivity analysis of the theoretical and statistical models showed that the statistical models fairs poorly under extrapolation. Additionally, the mechanistic causes of pump failure as well as the effect of heat and pumping head on water pumping performance were identified. Thereafter, the water collection efficiency was established to be 98% on average. Further testing revealed that the pumping performance of larger area or multiple grouped “leaves” are less accurately predicted with the theoretical model than a single “leaf”. In conclusion, the results provide some support that the surface tension driven pump may be used as a water transport system in an artificial photosynthesis project, if the functional lifespan of the pump can be greatly improved. It is recommended that a more rigid hydrophilic material be used in the “leaf” interface and that multiple narrower conduits be used instead of a single larger pipe. Additional future work may include the development of pit-like structures to prevent air spreading throughout the system as well as a simple mechanism for evaporative control. / AFRIKAANSE OPSOMMING: Die doel van hierdie ondersoek is om 'n oppervlakspanning-aangedrewe waterpomp te bou en te toets. Die oppervlakspanning-aangedrewe waterpomp is ‘n passiewe waterpomp wat gebruik maak van ‘n meganisme soortgelyke aan dié van bome om water te pomp. Hierdie ondersoek is by die Departement Meganiese en Megatroniese Ingenieurswese by die Universiteit van Stellenbosch uitgevoer. Vir die ondersoek is 'n uitgebreide literatuurstudie gedoen wat aspekte soos water eienskappe, oppervlakspanning (basiese beginsels, kapillêre kragte, die uitwerking van temperatuur, onsuiwerhede asook benatbaarheid), lugborrelvorming (kernvormingsteorie en die treksterkte van water) en uiteindelik water- en mineraalvervoer in bome (plantstrukture en -meganismes, beperkende faktore, wanpersepsies en die vervoer van organiese stowwe) insluit. Vorige navoring deur plantkundiges, wat die watervervoermeganismes in bome demonstreer, is ook in ag geneem. Die ondersoek het die ontwikkeling van 'n teoretiese termies-hidrouliese model ingesluit, wat gebruik is om die oppervlakspanning-aangedrewe waterpomp se werking te voorspel. Die waterpomp is ook eksperimenteel getoets met die fokus op ontwerpverbetering, pompwerkverrigting, pompwerking, potensiële pompopvoerdrukhoogte sowel as die waterversamelingsvermoë. Die eksperimentele data is statisties ontleed deur middel van meervoudige liniêre regressie. Beide die eksperimentele data en statisties-gegenereerde voorspellings is vergelyk met die teoretiese termies-hidrouliese-model. Die resultate toon dat 'n werkende oppervlakspanning-aangedrewe pomp gebou is. ‘n Verdampingstempo van tot 400 mL/hr.m2, pompopvoerdrukhoogte van tot 1.8m en 'n maksimum funksionele pompleeftyd van 13 dae is bereik. Die resultate dui verder daarop dat daar 'n goeie korrelasie tussen die verskillende statistiese lynpassings en die eksperimentele data is. Die teoretiese termies-hidrouliese-model wat ontwikkel is, toon 'n goeie ooreenkoms met die eksperimentele resultate. 'n Sensitiwiteitsanalise van die teoretiese en statistiese modelle het getoon dat die statistiese modelle swak voorspellings maak as geëkstrapoleerde data gebruik word. Verder is die meganismes wat pompweiering veroorsaak, die effek van hitte asook die effek van pompopvoerdrukhoogte op die pomp se werkverrigting geïdentifiseer. Daarna is die doeltreffendheid van waterversamelingsvermoë vir die waterpomp vasgestel op gemiddeld 98%. Verdere toetse het getoon dat die pompwerkverrigting van groter gegroepeerde "blare" minder akkuraat met die teoretiese model voorspel word as vir 'n enkele "blaar". Ten slotte: Die resultate toon dat die oppervlakspanning-aangedrewe waterpomp as 'n water vervoer stelsel gebruik kan word in 'n kunsmatige fotosinteseprojek, indien die funksionele leeftyd van die pomp verbeter kan word. Dit word aanbeveel dat 'n sterker hidrofiliese materiaal in die "blaar"-koppelvlak gebruik word en dat verskeie nouer leipype gebruik word in plaas van 'n enkele groter pyp. Bykomende toekomstige werk kan die ontwikkeling van put-agtige strukture insluit wat die verspeiding van lug deur die hele stelsel voorkom, sowel as 'n eenvoudige meganisme wat die verdampingstempo beheer.

The mass transfer area of nine structured packings was measured as a function of liquid load, surface tension, liquid viscosity, and gas rate in a 0.427 m (16.8 in) ID column via absorption of CO₂ from air into 0.1 mol/L NaOH. Surface tension was decreased from 72 to 30 mN/m via the addition of a surfactant (TERGITOL[trademark] NP-7). Viscosity was varied from 1 to 15 mPa·s using poly(ethylene oxide) (POLYOX[trademark] WSR N750). A wetted-wall column was used to verify the kinetics of these systems. Literature model predictions matched the wetted-wall column data within 10%. These models were applied in the interpretation of the packing results. The packing mass transfer area was most strongly dictated by geometric area (125 to 500 m²/m³) and liquid load (2.5 to 75 m³/m²·h or 1 to 30 gpm/ft²). A reduction in surface tension enhanced the effective area. The difference was more pronounced for the finer (higher surface area) packings (15 to 20%) than for the coarser ones (10%). Gas velocity (0.6 to 2.3 m/s), liquid viscosity, and channel configuration (45° vs. 60° or smoothed element interfaces) had no appreciable impact on the area. Surface texture (embossing) increased the area by 10% at most. The ratio of effective area to specific area (a[subscript e]/a[subscript p]) was correlated within limits of ±13% for the experimental database: [mathematical formula]. This area model is believed to offer better predictive accuracy than the alternatives in the literature, particularly under aqueous conditions. Supplementary hydraulic measurements were obtained. The channel configuration significantly impacted the pressure drop. For a 45°-to-60° inclination change, pressure drop decreased by more than a factor of two and capacity expanded by 20%. Upwards of a two-fold increase in hold-up was observed from 1 to 15 mPa·s. Liquid load strongly affected both pressure drop and hold-up, increasing them by several-fold over the operational range. An economic analysis of an absorber in a CO₂ capture process was performed. Mellapak[trademark] 250X yielded the most favorable economics of the investigated packings. The minimum cost for a 7 m MEA system was around $5-7/tonne CO₂ removed for capacities in the 100 to 800 MW range. / text

Rhamnolipid (RL) biosurfactants have been considered "green" alternatives to synthetic surfactants. Here, systematic studies of monorhamnolipids (mRLs) and their synthetic analogues are performed to characterize their interfacial and solution behaviors as surfactants. Chemical structure-surface activity relationships of rhamnolipids were probed using surface tension measurements on RLs and a series of their synthetic analogues designed by "truncation modification." Based on our study on RLs and the rationally-designed RL analogues, the key structural factor responsible for the excellent surface activity performance of rhamnolipids is the presence of the rhamnose moiety in the headgroup. As a result, rhamnopyranosides (RhEs), the simplest surfactants with a rhamnose moiety in the headgroup, show surface activity comparable to the bioproduced mRLs. The purified mixture of mRLs harvested from Pseudomonas aeruginosa ATCC 9027 was mixed with a nonionic surfactant Tween-20 (TW) and studied by surface tension measurements at pH 8. The experimental values of CMC show deviation from the theoretical values predicted by ideal solution theory, which is hypothesized to be due to a shape change from rod-shaped to spherical as the mole fraction of TW is increased. The hypothesis about the shape change is supported by dynamic light scattering results, regular solution theory, and packing parameter theory. Polarization modulated-infrared reflection-absorption spectroscopy (PM-IRRAS) has been used to characterize the orientation of the synthetic rhamnolipid Rha-C18-C18 at the air-water interface. Although rhamnolipids exhibit pH-dependent micellization, their orientation at the air-water interface is not affected by pH. The average tilt angle of their alkyl chains is determined to be ~45° at a surface pressure π = 40 mN/m which decreases to 36° when Pb²⁺ is present in the subphase. Assisted by molecular modeling, the packing of mRLs at the air-water interface is believed to be dominated by the packing of their large hydrophilic headgroups. Finally, the adsorption isotherm of mRLs on hydrophobic polyethylene surfaces was generated by ATR-FTIR from solutions of different pH, which were then fit to a Frumkin adsorption model to yield the thermodynamic adsorption parameters, the adsorption equilibrium constant and the interaction parameter. mRLs strongly adsorb to d-PE, and the adsorption is pH dependent.