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PubMed1998

Measurements of Contact Angles between an Oil-Water Interface and a Fiber by the ACDPAC Technique.

The ACRPAC (Analysis of Capillary Rise Profile Around a Cylinder) method was modified and extended to measure the contact angles between an oil-water interface and a fiber. Basically, the accurate image of the partial capillary depression profile was acquired and digitized by applying computer digital image processing and analysis techniques. The contact angle was determined by finding the best fit of the theoretically predicted profile, i.e., the curve representing a solution of the Laplace equation of capillarity, to the physically observed liquid-liquid interface. This analysis of the capillary depression profile around a cylinder (ACDPAC) technique was used to measure the contact angles of different water-oil interfaces on cylindrical glass fibers pre-coated with FC725. The wettability of the fiber-water-oil systems with varying oil and aqueous phases was examined. In particular, the wetting effects of a cationic surfactant cetyltrimethylammonium bromide (CTAB) and an anionic surfactant sodium dodecyl sulfate (SDS) dissolved in the aqueous phase were studied by using the ACDPAC technique. The oil phases tested were two dimethyl siloxane liquids, silicone oil A-type and silicone oil B-type. Copyright 1998 Academic Press.

Journal Article↗

PubMed2000

Adsorption of Benzoic and 4-Heptylbenzoic Acid on Different Silica Substrates from Organic and Aqueous Solution.

In studies of the adsorption of surface-active molecules from organic phase on mineral surfaces in relation to wettability alterations, the system has normally been made water-free. However, since water is an inherent part of all oil-bearing formations, it is of interest to study adsorption in solid/water/oil systems. In this paper we therefore study the adsorption of benzoic (BzCOOH) and 4-heptylbenzoic (4-HBA) acid from organic solution on different silica substrates in the presence of water. The results show that the adsorption is enhanced in the presence of water and that 4-HBA has a higher affinity for the silica surface than does BzCOOH. Variations in the surface properties of the silica substrates had no significant effect on the adsorption. In studies of the adsorption of organic acids from aqueous phase, the acid has been added either as the corresponding acid salt or as the acid itself. However, the adsorption behavior of the acid salt is not necessarily representative of the adsorption behavior of the acid. To investigate this more closely, we studied the adsorption of benzoic acid added to water both as sodium benzoate (BzCOO(-)Na(+)) and as BzCOOH. The results revealed a significant increase in the maximum adsorption when BzCOO(-)Na(+) was used as adsorbate instead of BzCOOH. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Partial Wetting in Capillary Liquid Absorption by Limestones.

We report measurements of the capillary absorption (imbibition) of water, n-heptane, n-decane, n-dodecane, methanol, ethanol, propan-2-ol, and ethanol-water mixtures into a number of dry calcitic limestones. The data are analyzed on the basis of unsaturated flow theory to give values of sorptivity S for water and for each organic liquid at different temperatures. The results show that for the organic liquids S varies as (surface tension/viscosity)(1/2) but that for the water S is anomalously low, indicating partial wetting. The wettability of these limestones is discussed in relation to natural contamination of the pore surface. Copyright 2000 Academic Press.

Journal Article↗

PubMed2001

Interfacial Characteristics and Fracture Toughness of Electrolytically Ni-Plated Carbon Fiber-Reinforced Phenolic Resin Matrix Composites.

The electrolytic plating of metallic nickel on a carbon fiber surface has been carried out in order to improve the interfacial adhesion and the mechanical properties in carbon fiber/phenolic matrix composite systems. The surface and the mechanical interfacial properties of composites are characterized by X-ray photoelectron spectrometry (XPS), surface free energy, and the critical stress intensity factor (K(IC)). From the experimental results, it is clearly revealed that the oxygen functional groups and the metallic nickel on fibers largely affect the mechanical interfacial behavior of the composites, resulting in increased surface polarity, whereas the nitrogen functional groups have no effect. Also, a good correlation between surface oxygen functional groups and mechanical interfacial properties and between wettability and K(IC) is established and it is found that a 10 A m(-2) current density is the optimum condition for this system. Copyright 2001 Academic Press.

Journal Article↗

PubMed2002

Tailoring the properties of asymmetric cellulose acetate membranes by gas plasma etching.

Cellulose triacetate (CTA) ultrafilters and cellulose acetate blend (CAB) desalination membranes were treated with a radiofrequency gas plasma (tetrafluoromethane (CF(4)) or carbon dioxide (CO(2)), 47-49 W, 0.04-0.08 mbar). Treatment times were varied between 15 s and 120 min. The plasma-treated top layer of the membranes was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and contact angle measurements to obtain information about surface structure, chemistry, and wettability, respectively. The membrane properties (e.g., permeability, selectivity, fouling) were studied by waterflux measurements, molecular weight cutoff measurements, and fouling experiments with bovine serum albumin. CO(2) plasma treatment resulted in gradual etching of the membrane's dense top layer. Permeation and selectivity changed significantly for treatment times of 0-15 min for CTA and 5-60 min for CAB membranes. Moreover, CTA membranes were hydrophilized during CO(2) plasma treatment whereas CF(4) plasma treatment led to hydrophobic surfaces due to strong fluorination of the top layer. This study shows that gas plasma etching can tailor the properties of asymmetric cellulose acetate membranes by simultaneously modifying the chemistry and structure of the top layer. The low fouling properties of CTA membranes were thereby largely maintained.

Animals↗

PubMed2002

Synthesis and surface properties of environmentally responsive segmented polyurethanes.

Polyurethanes, containing well-defined assemblies of perfluoro-polyether (PFPE or hexafluoropropene oxide oligomer), polydimethylsiloxane (PDMS), and polyethylene glycol (PEG) segments, exhibit oleophobic, hydrophobic, and hydrophilic properties in response to the polarity of the contacting medium. These polymers were prepared by reacting hydroxy(polyethyleneoxy)-propylether-terminated PDMS block copolymer (HO-PEG-PDMS-PEG-OH) with 4,4'-methylene-bis(phenylene isocyanate) (MDI) in the presence of dibutyltin dilaurate catalyst, followed by reaction with 1,2-diol functional PFPE and chain extension with 2,2,3,3-tetrafluoro-1,4-butanediol (FB). The oleophobic and hydrophobic properties of the segmented polyurethanes (SPU) are due to the segregation of PFPE segments at the polymer-air interface. Wettability studies revealed that the same surface becomes hydrophilic, presumably due to the segregation of the PEG segments at the polymer-water interface. This hydrophobic-to-hydrophilic transformation of the surface prevails not only when the polymer is in contact with liquid water but with water vapor as well. The understanding of the reconstruction mechanism of this novel family of SPU surfaces would furnish valuable information for various applications where dynamic transformation of surface activity is desired.

Journal Article↗

PubMed2002

Influence of aqueous electrolytes on the wetting behavior of hydrophobic solid polymers-low-rate dynamic liquid/fluid contact angle measurements using axisymmetric drop shape analysis.

The interaction of inorganic ions with low-energy hydrophobic surfaces was examined using model systems of solid polymers without ionizable functional surface groups in aqueous electrolyte solutions. Low-rate dynamic contact angle measurements with captive bubbles in conjunction with axisymmetric drop shape analysis (ADSA) were performed to study the influence of electrolyte ions (in the aqueous test solutions) on the wettability of the polymers. When various types of ions were used, no significant change in advancing and receding contact angles was observed. The contact angle hysteresis was small. The zeta potential of the model polymers in aqueous electrolyte solutions was determined from streaming potential measurements. The variation of the zeta potential at different pH levels indicates preferential adsorption of hydroxyl ions at this interface. However, the presence of electrolytes at the interface between water and the different model polymers did not influence the macroscopic contact angle. The results may suggest the absence of any specific interaction between the ions and the solid polymer, as this should result in changes of hydrophobicity. Similar to the air/water interface, the composition and the potential of the polymer/water interface are obviously determined predominantly by the aqueous phase with only slight influence from the solid phase.

Journal Article↗

PubMed2002

Surface tension and its temperature coefficient of molten tin determined with the sessile drop method at different oxygen partial pressures.

The surface tension of molten tin has been determined by the sessile drop method at temperatures ranging from 523 to 1033 K and in the oxygen partial pressure (P(O(2))) range from 2.85 x 10(-19) to 8.56 x 10(-6) MPa, and its dependence on temperature and oxygen partial pressure has been analyzed. At P(O(2))=2.85 x 10(-19) and 1.06 x 10(-15) MPa, the surface tension decreases linearly with the increase of temperature and its temperature coefficients are -0.151 and -0.094 mN m(-1) K(-1), respectively. However, at high P(O(2)) (3.17 x 10(-10), 8.56 x 10(-6) MPa), the surface tension increases with the temperature near the melting point (505 K) and decreases above 723 K. The surface tension decrease with increasing P(O(2)) is much larger near the melting point than at temperatures above 823 K. The contact angle between the molten tin and the alumina substrate is 158-173 degrees, and the wettability is poor.

Journal Article↗

PubMed1993

Decontaminating pesticide protective clothing.

The review of recent work on the mechanisms of soil removal from textiles assists in understanding decontamination of pesticide protective clothing. The current work provides explanatory conclusions about residue retention as a basis of making recommendations for the most effective decontamination procedures. A caution about generalizations: Some pesticides produce very idiosyncratic responses to decontamination. An example is the paraquat/salt response. Other pesticides exhibit noticeable and unique responses to a highly alkaline medium (carbaryl), or to bleach (chlorpyrifos), or are quickly volatilized (methyl parathion). Responses such as these do not apply to other pesticides undergoing decontamination. Given this caution, there are soil, substrate, and solvent responses that do maximize residue removal. Residue removal is less complete as the concentration of pesticide increases. The concentration of pesticide in fabric builds with successive exposures, and the more concentrated the pesticide, the more difficult the removal. Use a prewash product and/or presoak. The surfactant and/or solvent in a prewash product is a booster in residue removal. Residues transfer from contaminated clothing to other clothing during the washing cycle. Use a full washer of water for a limited number of garments to increase residue removal. The hotter the washing temperature, the better. Generally, this means a water temperature of at least 49 degrees C, and preferably 60 degrees C. Select the detergent shown to be more effective for the formulation: heavy-duty liquid detergents for emulsifiable concentrate formulations and powdered phosphate detergents for wettable powder formulations. If the fabric has a soil-repellent finish, use 1.25 times the amount recommended on the detergent label. For water hardness above 300 ppm, an additional amount of powdered phosphate detergent is needed to obtain the same level of residue removal as obtained with the heavy-duty liquid detergent when laundering fabrics with the soil-repellent finish. The mechanical action of agitation increases dislodgement of particulate material. Too many items in the washing apparatus or too low water volume, or both, decrease agitation and soil removal. Bleach can be used if desired. Fabric softener does not affect pesticide absorption or residue removal in laundering. Dry cleaning is not recommended because the solvents used in dry cleaning may be recycled through dilution, filtration, activated charcoal adsorption, or distillation. Pesticides still may be present in recycled solvents and can be transferred from one item to another, or from one load to subsequent loads of dry cleaning.

Decontamination↗

PubMed1995

Oral bioavailability of CHF1194, an inclusion complex of piroxicam and beta-cyclodextrin, in healthy subjects under single dose and steady-state conditions.

CHF1194 is an inclusion complex of beta-cyclodextrin with the nonsteroidal anti-inflammatory drug piroxicam. In man, beta-cyclodextrin acts as a carrier of piroxicam. As the inclusion complex of piroxicam-beta-cyclodextrin is wettable and more water soluble, the absorption rate of the drug is increased whilst its other pharmacokinetic characteristics remain unchanged. The aim of the present study in 12 healthy subjects was to compare the oral bioavailability of 20 mg piroxicam in a CHF1194 tablet and a plain piroxicam capsule after a single dose and after two weeks of once daily administration, and also to assess the plasma levels and urinary excretion of beta-cyclodextrin after CHF1194 administration. The two treatments were administered in cross-over fashion, separated by a wash-out period of three weeks. Piroxicam, 5'-hydroxypiroxicam and beta-cyclodextrin were monitored in plasma and urine for 120 h after the first and last doses. Clinical tolerance was excellent and no adverse event occurred during either phase of the study. The extent of absorption of piroxicam from the CHF1194 tablet after the single dose was equivalent to that after the plain piroxicam capsule, within confidence limits of less than 80-125%. After repeated dosing, CHF1194 yielded the same steady-state systemic concentrations of piroxicam and 5'-hydroxypiroxicam as the reference capsule, and similar excretion pattern of the metabolite. After both single and multiple dosing, piroxicam was absorbed more rapidly after CHF1194, an expected consequence of the complexation of piroxicam with beta-cyclodextrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1996

Carbaryl washoff from soybean plants.

Both the efficacy and fate of most foliar-applied pesticides may be affected by weather variables, especially rain. A multiple-intensity rainfall simulator was used to determine the effects of rainfall intensity and amount on concentrations of carbaryl (Sevin(R) XLS Plus) washed from soybean plants. Two hours after carbaryl was applied at 1.12 kg/ha, 25 mm of rain was applied at intensities of 13.0, 27.4, 53.8, or 105.1 mm/h. About 67% of the carbaryl on the plants was washed off by 25 mm of rain. Rainfall intensity affected carbaryl concentrations in washoff; higher concentrations occurred at lower intensities. Even though the experimental conditions were designed for "worst-case" conditions, washoff patterns suggested improved carbaryl rainfastness when compared to carbaryl (formulated as a wettable powder) washoff from cotton plants in earlier studies. Rainfall amount had a greater effect on carbaryl concentrations in washoff than rainfall intensity.

Carbaryl↗

PubMedDate not supplied

Pesticide exposure to greenhouse handgunners.

The exposure of pesticide applicators in a commercial greenhouse facility was assessed. Data were collected from four handgunners who applied fluvalinate (insecticide), chlorpyrifos (insecticide), ethazol (fungicide), and dicofol (miticide). Potential exposure was measured with exposure pads placed outside all clothing of the applicator. Handwashes and air samples were also collected, as were pre- and post-exposure tank mixture samples. Pesticide penetration was measured with exposure pads placed inside protective clothing. When all exposure assessments were normalized for spray rate, it was determined that applicators were at significantly greater potential dermal risk (excluding hands) from fluvalinate. The normalized air samples showed significantly more exposure to the applicator from ethazol. Exposure to outside pads was primarily (84%) to the legs of the applicators. Ethazol penetrated Tyvek coveralls more readily than the other compounds. Tank mixture analyses suggested that the wettable powder formulations were not well-mixed.

Adult↗

PubMed1979

A seasonal comparison of parathion degradation on oranges in Arizona.

A study comparing the leaf residue decay of parathion wettable powder (8 lbs per acre) on oranges was carried out on neighboring plots in Arizona beginning in October, 1975, and February, 1976. While identical amounts of parathion were present immediately after spraying and the half-life of parathion was the same in both months, there was, on the average, more parathion residue during February. Graphs of parathion and paraoxon levels over time differed between months (in excess of sampling variability). This most likely was due to the daily influences of climatological variables which were obviously different in October and February.

Arizona↗

PubMed1988

Surface hydrophobicity and water transport of the toad urinary bladder: effects of vasopressin.

The present study investigated whether the hydrophobic properties (wettability) of the luminal surface of the toad urinary bladder might play a role in modulating water transport across this epithelium. In the absence of vasopressin (ADH), water transport across the tissue was low, while luminal surface hydrophobicity (water contact angle) was relatively high. Following stimulation by ADH, water transport increased and surface hydrophobicity decreased. The addition of indomethacin to inhibit ADH-induced prostaglandin synthesis did not reduce these actions of ADH. In an attempt to alter water transport in this tissue, a liposomal suspension of surface-active phospholipids was administered to the luminal surface. This addition had no detectable influence on the low basal rates of water transport, but blocked the ADH-induced stimulation of water transport. We suggest that surface-active phospholipids on the toad bladder luminal membrane may contribute to the hydrophobic characteristics of this tissue. ADH may act to decrease surface hydrophobicity, facilitating the movement of water molecules across an otherwise impermeable epithelium. This surface alteration may be associated with the appearance of water channels in the apical membrane.

Animals↗

PubMed1983

Cell culture on polymers prepared by radiation-induced polymerization of various glass-forming monomers.

The growth of cells on polymers prepared by the radiation polymerization of monomethacrylate and dimethacrylate was investigated. Cell growth was affected greatly by such properties of the polymers as water content, wettability, and porosity. Growth was promoted remarkably by rinsing the polymers with warm water at 60-70 degrees C and by irradiation of polymers with an electron beam. Cell growth decreased with increasing oxyethylene length (n) in the polymerized dimethacrylate of same series, CH2C(CH3)CO(OCH2CH2)nOCOC(CH3)CH2. A decrease in the hydrophilicity of the polymer increased cell growth rate. Formation of pore structures in the polymer films also increased the cell growth.

Animals↗

PubMed1979

Surface thermodynamics of leukocyte and platelet adhesion to polymer surfaces.

Adhesion of leukocytes and platelets to solid substrates of different surface tensions and hence different wettability is studied from a thermodynamic point of view. A simple thermodynamic model predicts that a cellular adhesion should increase with increasing surface tension of the solid substrate if the surface tension of the medium in which the cells are suspended is lower than the surface tension of the cells. If the surface tension of the suspending medium is higher than that of the cells, the opposite behavior is predicted. These predictions are borne out completely by neutrophil adhesion tests, where the surface tension of the aqueous suspending medium is varied by addition of dimethyl sulfoxide (DMSO). Platelet adhesion experiments also confirm these predictions, the only difference being that surface tensions of the suspending medium above that of the platelets cannot be realized, owing to exudation of surface active solutes from the platelets. Utilization of the thermodynamic prediction that cellular adhesion should become independent of the surface tension of the substrate when the surface tensions of the cells and that of the suspending medium are equal leads to a value of the surface tension of neutrophils of 69.0 erg/cm(2), in excellent agreement with the value obtained from contact angles measured on layers of cells.

Cell Adhesion↗

PubMedDate not supplied

Effect of PEG 4000 on the dissolution rate of naproxen.

Naproxen is a nonsteroidal anti-inflammatory drug characterized by its low wettability and poor water solubility. Solid dispersions naproxen:PEG 4000 have been prepared in order to improve the solubility and dissolution rate of the drug, since these factors can be the limiting steps for absorption and bioavailability of poorly soluble drugs. X-ray diffraction analysis, infrared spectroscopy and differential scanning calorimetry detected no physico-chemical interaction between the drug and the inert carrier PEG 4000. The phase diagram of the naproxen-PEG 4000 system produced by DSC and hot stage microscopy is reported. The intrinsic dissolution rate of naproxen is calculated. The dissolution kinetics of solid dispersions prepared by the solvent and melt methods are compared with those of free drug and physical mixture. The studies were carried out at 37 degrees C and pH 1.2 according to the dispersed amount method. The dissolution profiles obtained indicate that a significant dissolution enhancement occurs with solid dispersions in comparison with the physical mixture. In addition, the physical mixture showed a dissolution rate higher than the free drug. Dissolution rate constants were determined by fitting the experimental data to the cube root function, to get straight line plots.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2003

In vitro dermal penetration study of carbofuran, carbosulfan, and furathiocarb.

In this study, the dermal penetration rate of carbofuran, carbosulfan, and furathiocarb has been measured with rat abdominal skin using the static diffusion cell. The technical grades of three compounds were applied at different doses on skin surface mounted in static diffusion cell and incubated at 32 degrees C for 48 h with shaking. The same procedures were carried out with furathiocarb EC (emulsifiable concentrate) and WP (wettable powder). At regular intervals, the receptor fluid in cell was sampled and analyzed by HPLC. Only carbofuran was found in carbosulfan- or furathiocarb-treated samples, suggesting they converted into carbofuran while passing through the skin layer. The quantity of insecticide penetrating skin increased with time and applied dose. The skin penetration rate increased with the water solubility of insecticides. The dermal penetration rates of carbofuran, furathiocarb, and carbosulfan were determined as 1.05 micro g/cm(2) per h ( r(2)=0.991), 0.46 micro g/cm(2) per h ( r(2)=0.984) and 0.14 micro g/cm(2) per h ( r(2)=0.967), respectively. There was no significant difference in rate of skin penetration between furathiocarb EC (1.42 micro g/cm(2) per h, r(2)=0.988) and WP (1.35 micro g/cm(2) per h, r(2)=0.982), while furathiocarb technical grade showed a lower skin penetration rate. In vitro models may be used to predict percutaneous absorption and are useful in selecting safer formulations for field application of pesticide.

Administration, Cutaneous↗