Spreading Pressure Research Articles

Dynamic Model of Material Deforming Under Microgrinding

Model of the process of the dynamic contact interaction of a single abrasive grain with processed material was generated on the basis of the microgrinding process physical parameters analysis. Model is implemented on the basis for the finite elements method, using LS-DYNA software. Following is considered to be condition of destruction - achieving limit deformation of the element with further removing the element.Suggested model is universal in relation to materials under examination, which contact is simulated. If we know strength parameters of the specific processed material and a single grain, we can calculate stresses and deformations in the sample and cutting forces components on a single grain.Performed calculations resulted in obtaining new data on spreading stress and pressure fields in a sample, as well as cutting forces components values on a single grain.

Moisture Sorption Isotherm of Preconditioned Pressure Parboiled Brown Rice

The pressure parboiling of paddy was carried out at 294.204 kPa for 7 min and preconditioning of brown rice was carried out in fluidized bed dryer at 60-80°C. The moisture sorption isotherms of pressure parboiled preconditioned brown rice at different salt concentrations (0, 2, 3, 3.5 and 4%) were obtained at 20 ± 1°C, 25 ± 1°C, and 30 ± 1°C. The experimental data of sorption isotherm were fitted with some of sorption models (GAB, MGAB, MCPE, MOSE, MHEE, and MHAE models). According to the statistical results, the MGAB model gave the best fit to the experimental sorption data and MHAE model was the least adequate. Sorption isotherm data were used to determine the some thermodynamic functions. The net isosteric heat of sorption was determined from the best fitting equation using the Claussius-Calpeyron equation. The net isosteric heat of sorption decreased with increasing moisture content and increased with increasing salt concentration same trend was observed in entropy of sorption. The spreading pressure increased with increasing water activity and salt concentration and decreased with increasing temperature. The net integral enthalpy decreased with increasing moisture content and increased with increasing salt concentration and reverse trend was observed in integral entropy.

실란처리 되어진 실리카가 첨가된 에폭시 접착제의 접착박리강도에 관한 연구

본 연구에서는 기존 에폭시수지에 에폭시 콩기름(Epoxidized soybean oil : ESBO)과 실란처리 되어진 실리카가 첨가된 에폭시 접착제의 접착특성에 대하여 고찰하였다. 실리카의 표면처리는 실란커플링제인 <TEX>${\gamma}$</TEX>-methacryloxy propyl trimethoxy silane (MPS), <TEX>${\gamma}$</TEX>-glycidoxy propyl trimethoxy silane (GPS), 그리고 <TEX>${\gamma}$</TEX>-mercapto propyl trimethoxy silane (MCPS)을 사용하였다. 실리카 첨가 에폭시 접착제의 표면특성과 구조특성은 scanning electron microscope (SEM)과 Fourier transform infrared spectroscopy (FT-IR)을 이용하여 관찰하였으며 T-peel 시험법에 의한 접착특성은 universal testing machine (UTM)를 이용하여 분석하였다. 실란처리에 따른 실리카의 평형 확산압력, 표면자유에너지, 비표면적은 BET법을 이용한 <TEX>$N_2$</TEX>/77 K 기체 흡착을 통하여 관찰하였다. 결과로서, 에폭시 접착제의 접착박리강도는 미처리에 비해 접착제 내 실란처리된 실리카가 함유됨에 따라 증가하였다. 이러한 결과는 실란커플링제가 에폭시 접착제의 분산을 증가시키는 중요한 역할이라고 판단된다. 그리고 MCPS로 실란처리한 에폭시 접착제의 경우 GPS와 MPS에 비해 가장 우수한 접착력을 나타냄을 확인하였다. In this paper, the effect of silane-treated silicas and epoxidized soybean oil (ESBO) addition on adhesion properties of silicas-filled epoxy adhesives was examined. The silicas were treated by <TEX>${\gamma}$</TEX>-methacryloxy propyltrimethoxy silane (MPS), <TEX>${\gamma}$</TEX>-glycidoxy propyl trimethoxy silane (GPS), and <TEX>${\gamma}$</TEX>-mercapto propyl trimethoxy silane (MCPS). Surface and structural properties of the adhesives were determined by using scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). The t-peel strength of the adhesives was estimated using the universal testing machine (UTM). And, the equilibrium spreading pressure, surface free energy, and specific surface area were investigated by BET methods with <TEX>$N_2$</TEX>/77 K adsorption. As a result, the peel strength of the adhesives was increased in the presence of silane-treated silicas in the adhesives compared to that of untreated silicas. This result indicated that the silane coupling agent played an important role in improving the dispersion of silicas in epoxy adhesives. And, the adhesives treated by MCPS were superior to the others in adhesion.

Moisture Adsorption Isotherms and Thermodynamic Properties of A uricularia auricula

Moisture adsorption isotherms of Auricularia auricula were determined using the gravimetric static method at 15–35C and within the range of 0.1–0.9 water activity. The adsorption data were fitted into eight isotherm models. The best fit of experimental data was obtained with GAB model in the range of temperatures and water activities investigated. The moisture adsorption isotherms obtained were type II sigmoid shape. The thermodynamic properties such as net isosteric heat, differential entropy and spreading pressure were also determined from moisture adsorption isotherm data of A. auricula. The net isosteric heat of adsorption and differential entropy decreased with increasing moisture contents. From the values obtained for net isosteric heat and differential entropy, it was verified that the enthalpy–entropy compensation theory could be applied, the process being carried out by enthalpy (Tβ > Thm). The spreading pressure increased with increasing water activity, and decreased with increasing temperature. Practical Applications Auricularia auricula, belonging to heterobasidiae of basidiomycetes and also called Jew's ear, wood ear, red ear, black tree fungus or ear fungus, is a nontoxic edible mushroom widely used in traditional Chinese cuisine and is known for their pharmaceutical effects in Chinese herbal medicine. Increasing attention has been paid to its exploitation and utilization in food industry. The objective of this study was to investigate the adsorption isotherms of A. auricula at 15C, 25C and 35C to select the most suitable model describing the isotherms, to determine the thermodynamic properties and to evaluate the application of the enthalpy–entropy compensation theory.

Moisture sorption isotherms and thermodynamic properties of Jack pine and palm wood: Comparative study

Currently, the impact of the controlled climate on moisture sorption isotherms of Jack pine and palm wood still remains unclear. The aim of this paper was to determine and compare the moisture sorption isotherms and thermodynamic properties of Jack pine and palm wood. The equilibrium moisture content of wood samples was measured within the range of 5 to 90% relative humidity at 50°C, 60°C, 70°C and 80°C. For both wood varieties, the equilibrium moisture content decreased with increasing temperature, however the effect of temperature is very remarkable for palm wood. The isosteric heat of desorption, the enthalpy and the entropy decreased with the increase of the moisture content. A good straight line correlated differential enthalpy and entropy, according to the enthalpy–entropy compensation theory. The spreading pressure decreased with increasing temperature at a given water activity, and increased with increasing water activity at a constant temperature. Predictive correlations of the two wood properties, based on experimental methods and physical laws, were established and compared.

Equilibrium spreading pressure and Langmuir–Blodgett film formation of omega-substituted palmitic acids

Langmuir–Blodgett isotherms and equilibrium spreading pressures were measured for compounds of the series X–(CH2)15COOH, X=CH3, SH, OH, F, Cl, Br. Only the CH3 and F terminated compounds formed monolayers with sufficient stability for accurate isotherm measurement, film transfer and X-ray photoelectron spectroscopic analysis. The presence of the terminal heteroatom substituents significantly diminished the stability of the L–B film and depressed the equilibrium spreading pressures (20°C) from 15.4mN/m for the CH3 terminated compound to a range of 0.95 to 0.08mN/m for the other members of the series. These characteristics are attributed to the monolayer film being in a metastable state and the dipole moment of the heteroatom terminal group increasing the monolayer film kinetic instability by facilitating the formation of three-dimensional structures.

Moisture Sorption Behavior and Thermodynamic Properties of Gulabjamun Mix

The equilibrium moisture contents of gulabjamun mix powder were determined at 10, 25 and 40C. The sorption isotherms of gulabjamun mix were of type II, with the sorption capacity decreasing with temperature. The Guggenheim–Anderson–de Boer best described the sorption data at all temperatures. The isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy were determined as a function of moisture content. The isosteric heat of sorption decreased with increasing moisture content, and it approached the latent heat of water at 15% moisture content. A plot of differential heat of sorption versus entropy satisfied the enthalpy–entropy compensation theory. The spreading pressures increased with increasing water activity but decreased with increasing temperature. The net integral enthalpy decreased with moisture content to a minimum value of −0.50 kJ/mol. The isokinetic temperature (Tβ) and harmonic mean temperature (Thm) values were determined as 339.5 and 297.5 K, respectively. Practical Applications The instant gulabjamun mix is a dry and convenient ready-to-use mix with long shelf life. In this study, the moisture sorption behavior and the thermodynamics of sorption of gulabjamun mix are presented. This work could be used as a reference to optimize the final moisture content of this product and specify its appropriate storage conditions. The sorption data will also be useful to predict the shelf life and stability of gulabjamun mix against deteriorative reactions.

Thermodynamic sorption properties of potato and sweet potato flakes

The moisture sorption isotherms of potato and sweet potato flakes were determined using a gravimetric method at 15, 20, 25 and 30°C for water activity ranging from 0.1 to 0.9. The GAB was found to be the most suitable for describing the relationship between equilibrium moisture content and water activity for the whole range of temperatures and relative humidities. The differential and integral thermodynamic functions of enthalpy and entropy were estimated from the sorption data for potato and sweet potato flakes. The differential enthalpy was determined using the Clausius–Clapeyron equation and decreased with increase in moisture content, the same behavior as found for differential entropy. From the values obtained for differential enthalpy and entropy, it was verified that the compensation theory could be applied, the process being carried out by enthalpy (Tβ>Thm) and non-spontaneous (ΔG>0). The spreading pressures increased with increasing water activity for all the temperatures studied. With respect to the integral properties, it was observed that the enthalpy increased with moisture content, but the entropy decreased. It was also shown that for the moisture range evaluated, the values for integral entropy were negative.

Mechanical stability of phase-segregated multicomponent lipid bilayers enhanced by PS-b-PEO diblock copolymers

Polymeric additives affect the mechanics of phospholipid vesicles, but little is known about the effect to supported lipid bilayers that are phase segregated on the submicron length scale. In this study, we use AFM-based force mapping, by means of breakthrough forces, to quantify the spreading pressures and line tensions of raft-forming lipid bilayers consisting of dioleoylphosphatidylcholine (DOPC), egg sphingomyelin (ESM), and cholesterol (Chol) in the presence of diblock copolymers comprised of polystyrene (PS) and poly(ethylene oxide) (PEO), PS-b-PEO. Varying molecular weights of PS-b-PEO were used in the experiments. The presence of the polymer leads to higher breakthrough forces when compared to pure DOPC/ESM/Chol bilayers. The lipid–polymer composite made with a PS block radius of gyration comparable to the bilayer thickness and a PEO block length that is the shortest exhibits the highest breakthrough forces and hence is the most stable mechanically. The breakthrough force distributions are analyzed to extract the spreading pressures and line tensions of the lipid–polymer composites. The spreading pressure is seen to increase with the addition of PS-b-PEO, and on average, increases with decreasing PEO block length. Based on the results, we propose the incorporation of the PS moiety into the bilayer core as the main mechanism of this enhanced resistance to bilayer breakthrough by the AFM tip.

Surface Reflectivity from Absorbed Films of Pulmonary Surfactant at the Air-Liquid Interface

Pulmonary surfactant (PS) is the complex mixture of lipids and proteins that forms a thin film on the liquid layer that lines the alveolar air-sacks of the lungs. When compressed by the decreasing alveolar surface area during exhalation, the surfactant films reduce surface tension to exceptionally low levels. This behavior in situ contrasts with the performance of spread monolayers in vitro that contain the complete set of surfactant constituents, which collapse promptly when compressed below the equilibrium spreading pressure. The structural characteristics that provide the basis for this functional difference remain controversial. The studies here used X-ray reflectivity to compare the structure of adsorbed films and spread monolayers of extracted calf surfactant on the air-water interface. Our results show the presence in the adsorbed film of additional double layers of distinct electron densities underneath the interfacial monolayer. These results support previous evidence that adsorbed films of pulmonary surfactant have multilamellar thickness, and that the additional layers may have functional significance.

Formation of Dynamic Duolayer Systems at the Air/Water Interface by using Non-ionic Hydrophilic Polymers

The inclusion of a water-soluble polymer, poly(vinyl pyrrolidone) (PVP), into a surface active film composition before application to the water surface leads to the formation of a dynamic duolayer; a novel surface film system. This duolayer shows improved surface viscosity over the monolayer compound alone, while the addition of polymer maintains other film properties such as evaporation control and equilibrium spreading pressure. Brewster Angle Microscopy shows that the duolayer film undergoes a different formation mechanism upon film compression, and the resultant surface pressure/area isotherm is different at lower surface pressures indicating the PVP is present on the water surface at these pressures and squeezed out to the water subphase at higher pressures. The addition of water-soluble polymers to form a dynamic duolayer provides a unique way to produce defect-free and tightly packed films while polymer is associated with the film. This finding provides new knowledge for the design of surface films with improved properties with potential applications in many areas.

Vertical spreading of two-dimensional crystalline colloidal arrays

We report on a novel self-driven climbing of two-dimensional (2-D) ordered monolayer crystalline colloidal arrays (CCAs). This phenomenon can be used to rapidly and efficiently prepare large area, highly ordered 2-D array monolayer CCA films on various substrates. Large area 2-D polystyrene (PS) particle CCAs were fabricated on water surfaces by a needle tip flow technique. Introduction of a wet substrate through the 2-D particle monolayer array on the water surface causes the 2-D array to flow onto the wet substrate surface due to a surface spreading pressure. This method can quickly prepare ordered 2-D particle arrays on numerous wet substrates including flat/curved glass slides, inner walls of glass tubes, hydrogels, flexible polymer films, patterned surfaces, etc. By using responsive hydrogels as substrates, we can conveniently prepare 2-D photonic crystal sensors that can be used to visually determine analyte concentrations. For example, we prepared 580 nm PS 2-D arrays on poly(2-hydroxyethyl methacrylate) hydrogels to sense ethanol in water.

Skimming behaviour and spreading potential of Stenus species and Dianous coerulescens (Coleoptera: Staphylinidae)

Rove beetles of the genus Stenus Latreille and the genus Dianous Leach possess pygidial glands containing a multifunctional secretion of piperidine and pyridine-derived alkaloids as well as several terpenes. One important character of this secretion is the spreading potential of its different compounds, stenusine, norstenusine, 3-(2-methyl-1-butenyl)pyridine, cicindeloine, α-pinene, 1,8-cineole and 6-methyl-5-heptene-2-one. The individual secretion composition enables the beetles to skim rapidly and far over the water surface, even when just a small amount of secretion is emitted. Ethological investigations of several Stenus species revealed that the skimming ability, skimming velocity and the skimming behaviour differ between the Stenus species. These differences can be linked to varied habitat claims and secretion saving mechanisms. By means of tensiometer measurements using the pendant drop method, the spreading pressure of all secretion constituents as well as some naturally identical beetle secretions on the water surface could be established. The compound 3-(2-methyl-1-butenyl)pyridine excelled stenusine believed to date to be mainly responsible for skimming relating to its surface activity. The naturally identical secretions are not subject to synergistic effects of the single compounds concerning the spreading potential. Furthermore, evolutionary aspects of the Steninae's pygidial gland secretion are discussed.

Rational design of monolayers for improved water evaporation mitigation

Seven chemically designed monolayer compounds were synthesized and investigated with comparison to the properties and water evaporation suppression ability of 1-hexadecanol and 1-octadecanol. Increasing the molecular weight and polarity of the compound headgroup drastically altered the characteristics and performance of the monolayer at the air/water interface. Contrary to the common expectation the monolayer's lifetime on the water surface decreased with increasing number of ethylene oxy moieties, thus optimal performance for water evaporation suppression was achieved when only one ethylene oxy moiety was used. Replacing the hydroxyl headgroup with a methyl group and with multiple ethylene oxy moieties resulted in a loss of suppression capability, while an additional hydroxyl group provided a molecule with limited performance against water evaporation. Theoretical molecular simulation demonstrated that for exceptional performance, a candidate needs to possess a high equilibrium spreading pressure, the ability to sustain a highly ordered monolayer with a stable isotherm curve, and low tilt angle over the full studied range of surface pressures by simultaneously maintaining H-bonding to the water surface and between the monolayer chains.

Application of Sessile Drop Method to Determine Surface Free Energy of Asphalt and Aggregate

Abstract Surface free energy is an important parameter to determine the work of adhesion between the asphalt binder and the aggregate, which is related to the moisture damage of asphalt mixture. In this study, the sessile drop technique was performed to obtain the contact angle between asphalt/aggregate and different probe liquids. The surface free energies of asphalt and aggregate were characterized on the basis of the Owens-Wendt’s theory. It was found that the sessile drop technique is a convenient way to determine the static contact angle. A test procedure was developed to offer a clear method to prepare the sample and measure the contact angle. The surface free energy of aggregate determined in this study was found to be smaller than that measured in other techniques because of equilibrium spreading pressure. The work of adhesion calculated from surface free energy can be utilized to choose the best combination of asphalt and aggregate, which can work as a reference in the selection of materials. Meanwhile, it was found that for the same aggregate, the pull-off strength and the work of adhesion of each asphalt-aggregate have the same trend of ranking.

Thermodynamic Analysis of Moisture Sorption Characteristics of Cheese-PuriMix

Sorption data were determined by static gravimetric method for cheese–puri mix at 25, 35 and 45C. The Guggenheim-Anderson-deBoer (GAB), Caurie, Henderson, Oswin and Smith isotherm models were attempted to describe the experimental data and were found to describe the sorption behavior of the product adequately. The solid surface area of the product was computed based on the GAB model monolayer moisture contents of the product and was found to increase with temperature. Thermodynamic properties of the product, including the isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy, were determined as a function of the product moisture content. Application of the enthalpy–entropy compensation theory to the sorption data revealed that the process was enthalpy-driven. The net integral enthalpy and entropy were found to decrease with increasing moisture content and were described as a function of the equilibrium moisture content using a power model. Practical Applications Sorption isotherms are important tools for food scientists to understand the behavior of a food product, especially low-moisture foods, toward the moist air that envelopes its surroundings. They are particularly useful to predict the physical, chemical and microbial stability of the product during storage and reconstitution. Thermodynamic properties of the product provide an insight into the energy requirement associated with moisture sorption and the temperature dependence of water activity. Cheese–puri mix is a value-added convenience dairy product, and information on its sorption characteristics would be useful to monitor its quality and shelf stability.

Mechanistic Studies of Particulate Soil Detergency: II: Hydrophilic Soil Removal

AbstractIn this work, the removal mechanism of kaolinite and ferric oxide (model hydrophilic particulate soils) from hydrophilic (cotton) and hydrophobic (polyester) fabrics was studied using three surfactant types: sodium dodecyl sulfate (SDS), octylphenol ethoxylate (OP(EO)10), and cetyltrimethylammonium bromide (CTAB). This work investigated the relations between zeta potential, surfactant adsorption, contact angle, solid/liquid spreading pressure, and dispersion stability in washing solutions as compared to detergency performance and antiredeposition as a function of surfactant concentration and pH level. The SDS showed the best detergency for both particulate soils, followed by OP(EO)10, with CTAB being the least effective surfactant. For SDS, the electrostatic repulsion between fabric and soil was found to be the dominant force for hydrophilic particulate soil removal. For the nonionic surfactant OP(EO)10, electrostatics are also important and steric effects aid particulate soil detergency. Electrostatic forces and solid/liquid interfacial tension reduction aids CTAB detergency. These same detergency mechanisms have previously been found for the case of hydrophobic soil removal from fabrics. Dispersion stability did not prove to be a dominant mechanism governing particulate soil detergency. From the SEM photos of soiled fabric, ferric oxide attaches to the fabric surface with no entrapment between fabric yarns; moreover, ferric oxide tends to form larger aggregates on cotton compared to polyester fabric. The adhesion of larger particles is hypothesized to be weaker than the smaller ones. Therefore ferric oxide can be more easily removed from cotton fabric than polyester. The SEM photos for kaolinite show little visual difference in particle agglomeration on polyester compared to cotton. Removal of kaolinite from cotton was found to be higher than from polyester, but there is less difference than for ferric oxide.

Moisture Sorption Thermodynamics of Camellia oleifera

Moisture sorption isotherms of shelled and unshelled Camellia oleifera were determined using a gravimetric static method at 20, 30 and 40 °C with water activity ranging from 0.111 to 0.976. Estimated parameters and fitting ability of seven models were evaluated, and the Peleg model provided the best description of the experimental sorption behaviour. The experimental data and the models were also used to obtain thermodynamic functions. The differential enthalpy decreased rapidly as the moisture content increased, when the moisture content exceeded 7 % (dry basis) the value of differential enthalpy tended to zero. The differential entropy showed similar trends. Spreading pressure increased with increasing water activity and decreased with increasing temperature at a given water activity. Net integral enthalpy increased slightly with moisture content to a maximum value, and thereafter decreased with increasing moisture content. However, net integral entropy decreased gradually with increasing moisture content, until reach to a minimum value and then increased slightly with further increases in moisture content.

DESORPTION ISOTHERMS AND THERMODYNAMIC PROPERTIES OF FRESH AND OSMOTIC-ULTRASONIC DEHYDRATED QUINCES

Experiments were conducted to determine the effect of pretreatment osmotic– ultrasonic dehydration on the desorption isotherms of quince by static gravimetric method at 30, 45 and 60C temperatures. The isotherms exhibited type II behavior, with the sorption capacity decreased with increasing temperature. Out of the six equilibrium sorption models that were evaluated, the Peleg equation gave the best fit to the sorption data. The Hasley equation was further used to estimate the thermodynamic functions (such as net isosteric heat, enthalpy–entropy compensation and spreading pressure) of quince. The net isosteric heat of sorption and differential entropy decreased with increasing moisture contents in an exponential function. A plot of differential heat versus entropy satisfied the enthalpy–entropy compensation theory. The spreading pressure increased with increasing water activity and decreased with increasing temperature. The value of net isosteric heat, differential entropy and spreading pressure of untreated samples are higher than that pretreated sample quince.

Dynamic Molecular Behavior of Semi-Fluorinated Oleic, Elaidic and Stearic Acids in the Liquid State

Ordinary fatty acids such as oleic, elaidic and stearic acids exist as their hydrogen-bonded dimers in their liquids and in non-polar solvents. Infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy have revealed that semi-fluorinated (SF) acids containing a perfluorooctyl group (C₈F₁₇) as a terminal segment exist also as hydrogen-bonded dimers, which are the units of inter- and intramolecular movements in their liquids and CCl₄. The dynamic molecular properties, such as self-diffusion coefficients and intramolecular movements of SF-oleic, SF-elaidic, and SF-stearic acids were compared with those of corresponding ordinary fatty acids (H-acids). From the high equilibrium spreading pressures (ESPs) for SF-acids compared with those for their corresponding H-acids, it was expected that the inter-acyl chain interaction is weaker for the SF-acid than for the H-acid: the SF-fatty acids should have higher molecular mobility than the corresponding ordinary H-acids in the liquid state. However, the self-diffusion coefficients obtained for SF-acids were smaller than those for the corresponding H-acids; the apparent activation energies for the self-diffusion process (translational movement) of SF-acids were larger than those for the corresponding H-acids. Namely, the motion of SF-acid molecules in a liquid phase is rather restricted compared with H-acid in spite of lower inter-acyl chain interaction of SF-acid. This unexpected result suggests that the molecular motion of SF-acid in a liquid phase is not directly governed by inter-acyl interaction, but may be interpreted as a reptation movement of an acid molecule, which is related to intramolecular movement. In fact, low intramolecular movements for SF-acid were confirmed by ¹³C-NMR T₁ measurements.