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At least 19 recordsLinked to original sources
PubMed2006

Pulmonary toxicity study in rats with three forms of ultrafine-TiO2 particles: differential responses related to surface properties.

Surface properties are critical to assess effects of ultrafine-TiO(2) particles. The aim of this study was to assess lung toxicity in rats of newly developed, well characterized, ultrafine-TiO(2) particles and compare them to TiO(2) samples in two different size ranges and surface modifications. Groups of rats were intratracheally instilled with doses of 1 or 5mg/kg of either two ultrafine rutile TiO(2) particles (uf-1 or uf-2); rutile R-100 fine-TiO(2) (F-1); 80/20 anatase/rutile P25 ultrafine-TiO(2) (uf-3); or alpha-quartz particles. Phosphate-buffered saline (PBS) solution instilled rats served as vehicle controls. Following exposures, the lungs of PBS and particle-exposed rats were evaluated for bronchoalveolar lavage (BAL) fluid inflammatory markers, cell proliferation, and by histopathology at post-instillation time points of 24h, 1 week, 1 and 3 months. The ranking of lung inflammation/cytotoxicity/cell proliferation and histopathological responses was quartz>uf-3>F-1=uf-1=uf-2. Exposures to quartz and to a lesser degree, uf-3 anatase/rutile TiO(2) particles produced pulmonary inflammation, cytotoxicity and adverse lung tissue effects. In contrast, exposures to F-1 fine-TiO(2) particles or to uf-1/uf-2 ultrafine-TiO(2) particle-types produced transient inflammation. We conclude that differences in responses to anatase/rutile uf-3 TiO(2) particles versus the rutile uf-1 and uf-2 TiO(2) particles could be related to crystal structure, inherent pH of the particles, or surface chemical reactivity. Thus, based on these results, inhaled rutile ultrafine-TiO(2) particles are expected to have a low risk potential for producing adverse pulmonary health effects. Finally, the results demonstrate that exposures to ultrafine-TiO(2) particle-types can produce differential pulmonary effects, based upon their composition, and crystal structure. Thus, the lung toxicity of anatase/rutile uf-3 should not be viewed as representative for all ultrafine-TiO(2) particle-types.

Animals↗
PubMed2006

Comparative evaluation of adhesion, surface properties, and surface protein composition of Listeria monocytogenes strains after cultivation at constant pH of 5 and 7.

AIMS: To analyse the cellular mechanisms that influence Listeria monocytogenes adhesion onto inert surfaces under acidic growth conditions. METHODS AND RESULTS: The adhesion capability of all the strains was significantly reduced after cultivation at constant pH 5 than at constant pH 7 and the cell surface was significantly less hydrophobic at pH 5 than at 7. At pH 5, the analyses of surface protein composition revealed that the flagellin was downregulated for all strains, which was confirmed by the absence of flagella and the P60 protein was upregulated for L. monocytogenes EGD-e, X-Li-mo 500 and 111. The use of L. monocytogenes EGD mutants revealed that flagellin could be involved in the adhesion process, but not P60 protein. It was also observed that the hydrophobic character was not linked to the presence or the absence of flagellin or P60 protein at the cell surface of L. monocytogenes. CONCLUSIONS: The decrease of L. monocytogenes adhesion at pH 5 could be attributed to the downregulation of the flagellin synthesis under the acidic conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: Conservation of food product at pH 5 will delay bacterial adhesion and biofilm formation during food processing on inert surfaces when the product is contaminated with L. monocytogenes.

Bacterial Adhesion↗
PubMed2005

Morphological specificity of yeast and filamentous Candida albicans forms on surface properties.

Physicochemical surface properties of Candida albicans were assessed from microbial adhesion to human epithelial cells and to octane droplets. The adherence of cells demonstrated the occurrence of morphological specificity for these adhesion assays. Filamentous forms exhibited adherence third times higher compared to budding forms, while their electrophoretic mobilities were comparable. Force measurements performed on filamentous form by AFM demonstrated that such adhesion was associated with microfibrillar surface structure.

Algorithms↗
PubMed1986

Studies on surface properties of asbestos. II. Role of dimensional characteristics and surface properties of mineral fibers in the induction of pleural tumors.

In animal experiments, the probability that pleural tumors will develop after mineral fiber implantation is dependent upon the fiber's size. This was originally analyzed in relation to the number of injected fibers with specific dimensional characteristics and, more recently, in relation to average aspect ratio (average length/diameter ratio). New experimental data on various mineral fibers suggest that the carcinogenic potency of a solid particle depends on two parameters: the nature of the mineral and therefore the nature of active surface sites, and the aspect ratio of the particle. These two parameters can intervene in a mechanism of model reaction involving the basic properties of lateral faces of fibers.

Animals↗
PubMed1999

Cell surface analysis techniques: What do cell preparation protocols do to cell surface properties?

Cell surface analysis often requires manipulation of cells prior to examination. The most commonly employed procedures are centrifugation at different speeds, changes of media during washing or final resuspension, desiccation (either air drying for contact angle measurements or freeze-drying for sensitive spectroscopic analysis, such as X-ray photoelectron spectroscopy), and contact with hydrocarbon (hydrophobicity assays). The effects of these procedures on electrophoretic mobility, adhesion to solid substrata, affinity to a number of Sepharose columns, structural integrity, and cell viability were systematically investigated for a range of model organisms, including carbon- and nitrogen-limited Psychrobacter sp. strain SW8 (glycocalyx-bearing cells), Escherichia coli (gram-negative cells without a glycocalyx), and Staphylococcus epidermidis (gram-positive cells without a glycocalyx). All of the cell manipulation procedures severely modified the physicochemical properties of cells, but with each procedure some organisms were more susceptible than others. Considerable disruption of cell surfaces occurred when organisms were placed in contact with a hydrocarbon (hexadecane). The majority of cells became nonculturable after air drying and freeze-drying. Centrifugation at a high speed (15,000 x g) modified many cell surface parameters significantly, although cell viability was considerably affected only in E. coli. The type of washing or resuspension medium had a strong influence on the values of cell surface parameters, particularly when high-salt solutions were compared with low-salt buffers. The values for parameters obtained with different methods that allegedly measure similar cell surface properties did not correlate for most cells. These results demonstrate that the methods used to prepare cells for cell surface analysis need to be critically investigated for each microorganism so that the final results obtained reflect the nature of the in situ microbial cell surface as closely as possible. There is an urgent need for new, reliable, nondestructive, minimally manipulative cell surface analysis techniques that can be used in situ.

Bacterial Adhesion↗
PubMed2006

Surface properties and behaviour on abiotic surfaces of Staphylococcus carnosus, a genetically homogeneous species.

This work aimed to characterize the surface properties of Staphylococcus carnosus and the influence of different media on their ability to adhere and grow on industrial supports. As their colonization could be dependant of the strain, the genetic diversity of the strains was studied. The diversity of 13 strains analysed by pulsed-field gel electrophoresis revealed that the S. carnosus strains formed a homogeneous genetic group. Their surface properties, characterized by studying their affinity to solvents, were hydrophilic with a strong negative surface charge. The S. carnosus strain CIT 833 hardly adhered to polytetrafluoroethylene (PTFE) and stainless steel chips. Tryptic soy broth (TSB) was the most favourable medium for growth on stainless steel support while TSB/NaCl was better for growth on PTFE. Scanning electron microscopy (sem) showed that this strain weakly colonized both supports and did not form cell aggregates. Indeed, the strain did not synthesize polysaccharides. These results showed that S. carnosus adhered on different abiotic surfaces which are used in food factories but was not able to accumulate on these surfaces. The inability of S. carnosus to form biofilm could explain why S. carnosus is rarely isolated in meat processing environment.

Bacterial Adhesion↗
PubMed2002

The effect of disinfectants on the properties of dental gypsum, part 2: surface properties.

PURPOSE: This study is part of an ongoing investigation to evaluate the surface properties of dental stones mixed with disinfection solutions, and to determine the effect of adding gum arabic and calcium hydroxide on the same properties. MATERIALS AND METHODS: Aqueous solutions of 2 chemical disinfectants were used in mixing 2 types of dental stones (type III and type V). These dental stones were modified further by adding 1% gum arabic and 0.132% calcium hydroxide to their hemihydrate powders before mixing. Five specimens prepared from each type of dental stone were classified into 7 groups according to the hemihydrate powder modification and mixing liquid/powder ratio. Surface roughness was tested by 2-dimensional profilometery and scanning electron microscopy (SEM). Knoop hardness testing was carried out, and detail reproduction was assessed using ADA specification 25 in addition to SEM and 3-dimensional profilometer studies. RESULTS: Dental stones mixed with chemical disinfectants showed higher average roughness (R(a)) values than those of the controls. However, adding gum arabic and calcium hydroxide to the hemihydrate powders before mixing restored values to the level of the control. The additives seemed to have a role in the improvement of surface hardness. There was no significant difference between the experimental and the control group in the terms of detail reproduction. CONCLUSIONS: Using SEM, 3-dimensional profilometry, and ADA testing methods, we found that the surface roughness of stone casts was adversely affected by using the disinfectant solutions as mixing water substitutes. Gum arabic and calcium hydroxide additives can yield a harder stone surface without compromising other surface properties.

Analysis of Variance↗
PubMed1998

Surface Properties of Fluorosilicone Copolymers and Their Surface Modification Effects on PVC Film.

The fluorosilicone copolymers were synthesized using a fluorine-containing monomer and silicone-containing monomers by free-radical random copolymerization, and their surface properties and surface modification ability were investigated. The fluorine-containing monomer used was perfluoroalkyl ethyl acrylate (FA), and the silicone-containing monomers used were 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (SiMA), vinyltrimethoxy silane (VTMS), and vinyltriethoxy silane (VTES). The surface free energies of the fluorosilicone copolymers prepared were estimated from the contact angle data measured by sessile-drop method. And, the surface free energies of poly(vinyl chloride) (PVC) films modified by the fluorosilicone copolymers were also analyzed using the contact angle data. The fluorosilicone copolymers exhibit the surface free energies of about 8-23 dyn/cm dependent on the molecular weight of the fluorosilicone copolymers. The surface free energies of the fluorosilicone copolymers decrease with increasing molecular weight in the range of 2,000-10,000 (Mw). Among the fluorosilicone copolymers prepared in this study, PFA-r-PSiMA was found to be the most effective as a surface modification agent for PVC film. The inherent surface free energy of PFA-r-PSiMA was estimated to be about 9.0 dyn/cm. The desirable molecular weight of PFA-r-PSiMA seems to be more than 4,000 (Mw). However, it is expected that the fluorosilicone copolymers having the molecular weight of much higher than 10,000 (Mw) may not be suitable as surface modification additives because their compatibility with other polymers will decrease with the molecular weight. The optimum concentration of PFA-r-PSiMA added to PVC film is about 1.0 wt.%. PFA-r-PSiMA is expectedto be an effective additive for surface modification of PVC films. Copyright 1998 Academic Press.

Journal Article↗
PubMed2004

Contribution of the comonomers to the bulk and surface properties of methacrylate copolymers.

Relationships between formulation, bulk properties, and surface properties are investigated on series of copolymers prepared with hydroxyethylmethacrylate (HEMA), methylmethacrylate (MMA), and ethylmethacrylate (EMA) monomers, and on the homopolymers PMMA and PHEMA. The bulk water content, swelling ratio, and static (sessile drop and captive bubble) and dynamic (Wilhelmy plate technique) contact angles and the electrokinetic potential (streaming potential) are measured. The bulk water content and swelling ratio of HEMA copolymers are proportional to the amount of HEMA and are linearly correlated to the contact angle hysteresis. Periodic instabilities in the wetting cycles, similar to Haines jumps, are observed with HEMA copolymers and support a bidirectional relaxation of the hydrophilic groups respectively towards external water and capillary water. The origin of the electrokinetic potential of these nonionizable polymers is attributed to specific adsorption of [Formula: see text] ions. Its dependence on surface hydrophobicity and statistical length of the side-chains is interpreted in terms of the properties of water molecules near the interface.

Journal Article↗
PubMed2005

Surface properties of mixtures of surface-active sugar derivatives with ionic surfactants: theoretical and experimental investigations.

Surface properties of systems that are mixtures of ionic surfactants and sugar derivatives-anionic surfactant sodium dodecyl sulfate and n-dodecyl-beta-D-maltoside (SDS/DM) and cationic surfactant dodecyltrimethylammonium bromide and n-dodecyl-beta-D-glucoside (DTABr/DG)-were investigated. The experimental results obtained from measurements of surface tension of mixtures with various ratio of ionic to nonionic components were analyzed by two independent theories. First is Motomura theory, derived from the Gibbs-Duhem equation, allowing for indirect evaluation of the composition of mixed monolayers and the Gibbs energies of adsorption, corresponding to mutual interaction between surfactants in mixed adsorbed film. As second theory we used our newly developed theoretical model of adsorption of ionic-nonionic surfactant mixtures. Using this approach, we were able to describe the experimental surface tension isotherms for mixtures of surface-active sugar derivatives and ionic surfactants. We obtained a good agreement with experimental data using the same set of model parameters for a whole range of studied compositions of a given surfactant mixture. The values of surface excess calculated from both theories agreed with each other with a reasonable accuracy. However, the newly developed model of adsorption of ionic-nonionic surfactant mixtures has the advantage of straightforward determination of surface layer composition. By the solution of equations of adsorption, one can obtain directly the values of surface excess of all components (surfactant ions, counterions, and nonionic surfactants molecules), which are present in the investigated system.

Journal Article↗
PubMed2004

In situ determination of the thermodynamic surface properties of chemically modified surfaces on a local scale: an attempt with the atomic force microscope.

We have monitored deflection-distance curves with an atomic force microscope (AFM) in contact mode, with a silicon nitride tip, on chemically modified silicon wafers, in the air. The wafers were modified on their surface by grafting self-assembled monolayers (SAMs) of different functional groups such as methyl, ester, amine, or methyl fluoride. A chemically modified surface with a functionalized hydroxyl group was also considered. Qualitative analysis allowed us to compare adhesive forces versus chemical features and surface energy. The systematic calibration procedure of the AFM measurements was performed to produce quantitative data. Our results show that the experimentally determined adhesive force or thermodynamic work of adhesion increases linearly with the total surface energy determined with contact angles measured with different liquids. The influence of capillary condensation of atmospheric water vapor at the tip-sample interface on the measured forces is discussed. Quantitative assessment values were used to determine in situ the SAM-tip thermodynamic work of adhesion on a local scale, which have been found to be in good agreement with quoted values. Finally, the determination of the surface energy of the silicon wafer deduced from the thermodynamic work of adhesion is also proposed and compared with the theoretical value.

Microscopy, Atomic Force↗
PubMed1998

Influence of surface properties at biodegradable microsphere surfaces: effects on plasma protein adsorption and phagocytosis.

OBJECTIVE: The objective of this work was to determine plasma protein adsorption and macrophage phagocytosis of biodegradable polyanhydride, polylactic acid and polylactic-co-glycolic acid microspheres prepared by both spray-drying and solvent evaporation techniques. METHODS: Microspheres were characterized by scanning electron microscopy (SEM), confocal laser microscopy, particle size distribution and zeta (zeta) potential determination. Plasma protein adsorption onto the microspheres was determined using a fluoroaldehyde reagent. Phagocytosis was evaluated by incubating microspheres containing the angiotensin II antagonist, L-158,809, with the macrophages in the presence or absence of the phagocytosis inhibitor cythochalasin D. The extent of phagocytosis was established by fluorescence determination of L-158,809 and by optical microscopy. The effect of amphiphilic poly(ethylene glycol) (PEG) derivatives on phagocytosis was determined using PEG-distearate incorporated into the microspheres. RESULTS: The average diameter of the microspheres, which depended on the polymer and the initial formulation, ranged from 0.9 to 3.2 micrometers. Zeta potential studies showed strong negative values irrespective of the polymer used for the spray-dried formulations. The zeta potential was masked by the incorporation of PEG 400- or PEG 1,400-distearate in the formulation. Confocal laser microscopy showed a homogenous dispersion of PEG (measured as PEG-fluorescein) in the microspheres. Protein adsorption was not observed for any of the microsphere formulations following incubation with bovine serum. Incubation of microspheres with murine macrophages showed that PEG-distearate inhibited phagocytosis at appropriate levels (0.1% w/w). Higher levels > 1% w/w of PEG-distearate) resulted in enhanced association with macrophages, despite the presence of the phagocytosis inhibitor cytochalasin D, indicating fusion between the microspheres and the plasma membrane. CONCLUSIONS: These results demonstrate that spray-dried PEG-containing microspheres can be manufactured and that an appropriate concentration of this excipient in microspheres results in decreased phagocytosis.

Adsorption↗
PubMed1998

Surface properties of native human plasma lipoproteins and lipoprotein models.

Plasma lipoprotein surface properties are important but poorly understood determinants of lipoprotein catabolism. To elucidate the relation between surface properties and surface reactivity, the physical properties of surface monolayers of native lipoproteins and lipoprotein models were investigated by fluorescent probes of surface lipid fluidity, surface lateral diffusion, and interfacial polarity, and by their reactivity to Naja melanoleuca phospholipase A2 (PLA2). Native lipoproteins were human very low, low-, and subclass 3 high-density lipoproteins (VLDL, LDL, and HDL3); models were 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or its ether analog in single-bilayer vesicles, large and small microemulsions of POPC and triolein, and reassembled HDL (apolipoprotein A-I plus phospholipid). Among lipoproteins, surface lipid fluidity increased in the order HDL3 < LDL < VLDL, varying inversely with their (protein + cholesterol)/phospholipid ratios. Models resembled VLDL in fluidity. Both lateral mobility in the surface monolayer and polarity of the interfacial region were lower in native lipoproteins than in models. Among native lipoproteins and models, increased fluidity in the surface monolayer was associated with increased reactivity to PLA2. Addition of cholesterol (up to 20 mol%) to models had little effect on PLA2 activity, whereas the addition of apolipoprotein C-III stimulated it. Single-bilayer vesicles, phospholipid-triolein microemulsions, and VLDL have surface monolayers that are quantitatively similar, and distinct from those of LDL and HDL3. Surface property and enzymatic reactivity differences between lipoproteins and models were associated with differences in surface monolayer protein and cholesterol contents. Thus differences in the surface properties that regulate lipolytic reactivity are a predictable function of surface composition.

Animals↗
PubMed1996

Correlation of drug absorption with molecular surface properties.

The correlation between dynamic surface properties of drug molecules and drug absorption in two common in vitro models of the intestinal wall (Caco-2 monolayers and rat intestinal segments) has been investigated. A homologous series of beta-adrenoreceptor antagonists were used as model compounds. Dynamic molecular surface properties, considering all low-energy conformations, of the compounds were calculated. The flexibility of the molecules was studied by molecular mechanics calculations (MM2) and the van der Waals' (vdW), and water accessible surface areas were calculated and averaged according to a Boltzmann distribution. Excellent correlations were obtained between the dynamic polar vdW surface areas and cell permeabilities in Caco-2 cells and rat ileum (r2 = 0.99 and 0.92, respectively). These correlations were stronger than those between calculated octanol/buffer partition coefficients (log Doct,7.4) and permeability (r2 = 0.80 and 0.73, respectively). Moreover, the calculated log Doct,7.4 values failed to rank the permeability coefficients through Caco-2 monolayers and rat ileum in the correct order. The results indicate that dynamic polar surface area is a promising alternative model for the prediction of oral drug absorption.

Adrenergic beta-Antagonists↗
PubMed1975

Abnormal membrane surface properties during maturation of rat reticulocytes elicited by bleeding as measured by partition in two-polymer aqueous phases.

Partition of cells in two-polymer aqueous phases is an extremely sensitive method for the separation of cells and for tracing subtle changes in the cells' membrane surface properties (primarily surface charge) as a function of in vivo processes (e.g. differentiation, maturation, ageing). Combining isotope labelling and cell countercurrent distribution techniques we have examined the membrane surface properties of rat reticulocytes produced in response to erythroid stress by bleeding. It was found that the rapid increase in the partition coefficient of normal reticulocytes subsequent to release into the peripheral blood (which reflects a rapid increase in membrane surface charge) is absent in reticulocytes produced in response to bleeding. In this way the reticulocytes behave like those produced in response to repeated phenylhydrazine injections. 'Stress reticulocytes' never mature to erythrocytes having normal membrane surface properties as judged by partition. The experiments show that our previous results are not due to the phenylhydrazine per se but rather to the production of 'stress reticulocytes'. Further, if remodelling of the phlebotomy-induced reticulocyte cell membrane occurs in the circulation as has been suggested it does not lead to a cell with normal membrane surface properties. Whether the abnormal membrane surface properties of 'stress reticulocytes' and of the erythrocytes to which they give rise affect the cells' life-span is not clear since phenylhydrazine-induced 'stress reticulocytes' have been reported to have at least a component of short-lived cells while the phlebotomy-induced cells are said to have a virtually normal life-span. It is likely that reticulocytes produced in severe anaemias, in general, mature to erythrocytes having abnormal surface properties (i.e. lower membrane surface charge).

Animals↗
PubMed1997

[Stimuli sensitive changes in electrical surface properties of soft membranes: from a synthesized polymer to a biological system].

The electrical surface properties of biological cells have been studied, which provided us with the fundamental knowledge about the cell surface. The change in shape or biological functions of cells may affect the surface properties and can be detected by electrokinetic measurements. Biological cell surfaces are covered with polysaccharide chains, some are charged and some are not. Some polysaccharides produce a hydrogel matrixes under a proper condition. We thus consider it reasonable that cell surface is approximated by a hydrogel surface. Electrophoretic mobility measurements are useful for studying the surface properties of biological cells suspended as colloidal particles in an electrolyte solution. The electro-osmotic velocity measurements on the other hand are advantageous to the study of the surface properties of slab-shaped biological systems such as membranes. This work was started with a hydrogel, as a model material. As a hydrogel, poly(N-isopropylacrylamide) poly(NIPAAm), abbreviated as hereafter, was chosen, because this hydrogel changes its volume depending on temperature. The dependence of the electrophoretic mobility of latex particles covered with poly(NIPAAm) hydrogel layer or of the electro-osmotic mobility on poly(NIPAAm) plate upon temperature and ionic strength of the dispersing medium was well explained with an electrophoretic mobility formula for "soft particles" developed by Ohshima. The electrokinetic measurements and the explanation of data with an electrophoretic mobility formula for "soft particles" give us information about the surface charge density and the "softness" of soft surfaces. On the basis of the findings with hydrogels, we have discussed the relationship between the changes in shape or function of the biological cells and the change in physicochemical surface properties using these measurements. To study the change in physicochemical properties of the cell surface caused by apoptosis, we have measured the electrophoretic mobilities of intact and apoptotic human promyelocytic leukemia cell lines, HL-60RG cells. We have also studied the differences observed in surface properties of malignant lymphosarcoma cell line, RAW117-P, and its variant, RAW117-H10, with a high metastatic property to the liver. In both cases, the cell surfaces became softer by the changes of biological functions. We have applied electrophoresis and electro-osmosis measurements to the study of the electrokinetic surface properties of rat basophilic leukemia cells, RBL cells. It was also found that the surface of Human umbilical vein endothelial cells, HUVEC, is considerably soft as compared with those of other biological cells we have studied before.

Acrylic Resins↗
PubMed1967

Effects of gestation and prenatal asphyxia on pulmonary surface properties of the foetal rabbit.

1. The pulmonary surface properties of foetal rabbits were studied after delivery by Caesarean section at 26-30 days and after normal delivery at term (31 days).2. Quasi-static pressure-volume curves were defined for the lungs and the surface properties of the same lungs were further studied both by the bubble-stability method and by means of a surface balance and trough. Results given by each method are compared and discussed.3. At the 26th day of gestation the pulmonary surface properties, characteristic of the animal at term, were not yet present. These properties were first evident on the 28th day.4. A period of 16 min intense prenatal asphyxia on the 28th day of gestation failed to produce a change in pulmonary surface properties.

Animals↗
PubMed2000

Surface Properties of Vitreous Fibers.

The surface properties of various vitreous fibers, suspected to be toxic to humans and animals, were investigated by means of paramagnetic labels covalently linked to the surface. Computer-aided analysis of the electron paramagnetic resonance (EPR) spectra provided structural and dynamic information on the label and its environment. Calorimetric measurements provided information on the hydration mechanism. The results were analyzed in terms of (a) different polarity and interaction abilities of surface regions, (b) presence of ions at the surface, (c) silica contents, (d) vicinity of the interacting sites, (e) fiber dimension and morphology of the surfaces, and (f) water hydration. The mobility of the labels decreased due to interaction of the fibers with ions or ionic and polar groups at the surface. Close interacting sites were identified on the basis of spin-spin effects and were distinguished and quantified in strongly and weakly interacting sites. The spin-labeling technique indicated decreased ability of the surface to interact with decreased silicon concentration and in the presence of contaminants at the surface. The interaction with water revealed in all cases a substantial heterogeneity in hydrophilicity of surface sites. The labels were not easily hydrated. Vitreous fibers of various compositions adsorbed much more water than crystalline or amorphous silica; water coordinated to surface cations played a major role in the overall adsorption. The surface reaction mechanisms were the same on fibers of different compositions, but the surface composition affected the extent of adsorption. Glass wool exhibited a much higher adsorption capacity than rock wool under the same experimental conditions. In conclusion, the combination of EPR and calorimetric measurements provided insight into the surface properties of silica-based fibers. Copyright 2000 Academic Press.

Journal Article↗