[Plastic repair of the seromuscular layer of the uterine wall with synthetic polymers. (Experimental study)].
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Animals↗
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Results for “Fluorocarbon Polymers”
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Investigation of fluorocarbon blowing agents in insulating polymer foams by 19F NMR imaging.
Currently, there is no reliable and readily accessible technique with which the distribution and diffusion of blowing agents in rigid insulating foams can be detected and monitored. In this paper, we demonstrate that 19F NMR microscopic imaging together with 19F solid-state MAS NMR spectroscopy is ideally suited for such measurements and yield quantitatively reliable information that will be critical to the development and fabrication of optimized insulating materials with alternative blowing agents. Polystyrene (PS) and polyurethane (PU) foam samples were investigated with the objective of determining quantitatively the amount of blowing agents in the gaseous phase and dissolved in the polymer phase, and to determine and monitor the distribution of the blowing agents in aged foams as a function of time and temperature. The concentrations of the gaseous blowing agents in the cells and dissolved in the solid were simultaneously and quantitatively measured by 19F MAS NMR spectroscopy. An unfaced 1-yr-old PS foam filled with CH3CF2Cl has about 13% of total HCFCs dissolved in the solid; while there is about 24% of HCFCs in the solid of a faced 3-mos-old PU foam filled with CH3CCl2F. The data from 19F NMR imaging demonstrate that the distributions of the blowing agents in an aged foam are quite uniform around the center part (2 cm away from any edge) of a foam board; however, a gradient in blowing agent concentration was found as a function of distance from the initial factory cut edge. The effective diffusion coefficients of the blowing agents can be directly calculated from the imaging data. Quantitative diffusion constants and activation barriers were determined. Additionally, a foam treated with a second blowing agent was monitored with chemical shift selective imaging and the diffusion of the second gas into the foam and the out-diffusion of the original gas were determined.
Construction Materials↗
On-chip high-pressure picoliter injector for pressure-driven flow through porous media.
A high-pressure (> 3 MPa) on-chip injector has been developed for microchip applications including HPLC. The mechanical injector is implemented using in situ photopolymerization of fluorinated acrylates inside wet-etched silica microchips. The injector allows reproducible injections as small as 180 pL with < 250 ms duration. The injector operated robustly over 60 days and over 1000 injections. The injector is unique among polymer-based valves as it functions in aqueous, acetonitrile, and mixed buffers at high pressures without detectable leakage.
Acrylates↗
Characterization of the solvation and transport of the hydrated proton in the perfluorosulfonic acid membrane nafion.
The solvation and transport properties of the sulfonate-hydronium ion pair have been studied in hydrated Nafion through molecular dynamics simulation. Explicit proton and charge delocalization of the excess proton transport, via the Grotthuss hopping mechanism, were treated using the self-consistent multistate empirical valence bond (SCI-MS-EVB) method. The nature of the sulfonate-hydronium ion pair was characterized through analysis of free-energy profiles. It was found that, in general, the excess proton is solvated between two water molecules of a Zundel moiety while in the contact ion pair position, but then it transitions to an Eigen-like configuration in the solvent-separated pair position. Furthermore, the positive charge associated with the excess proton passes between the contact and solvent-separated ion pair positions through the Grotthuss mechanism rather than simple vehicular diffusion. The total proton diffusion was decomposed into vehicular and Grotthuss components and were found to be of the same relative magnitude, but with a strong negative correlation resulting in a smaller overall diffusion. Correlated motions between the ion pair were examined through the distinct portion of the van Hove correlation function, and a characteristic time scale of approximately 425 ps was observed. Additionally, the association of the hydrated proton with the hydrophobic polymer backbone suggests its amphiphile-like behavior (see Acc. Chem. Res. 2006, 39, 143; Phys. Rev. 1954, 95, 249; J. Chem. Phys. 2005, 123, 084309).
Chemistry, Physical↗
Characterizing emission and breathing-zone concentrations following exposure cases to fluororesin-based waterproofing spray mists.
Measurements and simulations were performed to assess workers' exposure to solvent vapors and aerosols during the waterproofing of a tiled surface. This investigation followed two recent incidents in the same company where workers experienced acute respiratory illness after spraying a stain-repellent resin containing fluorinated polymers on stone-tiled walls and floors. Because the waterproofing activity had been done for years at the tile company without encountering any exposure problems prior to these cases, it was strongly suspected that the incidents were linked to a recent change in the composition of the coating mixture. Experimental measurements and simulations indicated that the emission rate of particles smaller than 10 microm may be estimated at 0.66 mg/sec (SD 0.10) for the old resin and at 0.37 mg/sec (SD 0.04) for the new one. The measurement of the solvent emission rate from surfaces coated with the two resins indicated that shortly after spraying, the emission was in the range of 18 to 20 mg/sec x m2 and was similar for both products. Solvent and overspray emission rates were introduced in a two-zone compartment model. The results obtained in the near-field indicate significant exposure to overspray mist (7 and 34 mg/m3 for new resin) and solvent vapors (80 to 350 ppm for the new resin). It was also shown that the introduction of the new resin tended to significantly decrease the levels of solvents and particulates in the workers' breathing zone. These results strongly suggest that cases of acute respiratory illness are related to the specific toxicity of the fluorinated polymer itself. The fact that the same polymer is used in various commercial products raises concern regarding other possible occupational and domestic exposures.
Acrylic Resins↗
[Pulmonary damage caused by ski waxing].
It is well known that inhalation of pyrolysis products of perfluorinated hydrocarbons (e.g. Teflon) may result in polymer-fume fever and even pulmonary oedema. A new type of ski wax has recently been introduced, a powder consisting of low-molecular perfluorinated hydrocarbons. We report a case history of a man who developed an attack of polymer-fume fever and pulmonary oedema after smoking cigarettes contaminated with this ski wax. Inhalation of vapour from ski waxes melted at low temperatures may also be harmful to the lungs.
Adult↗
Effect of hexafluoropropylene oxide plasma polymer particle coatings on the rheological properties of boron nitride/poly(dimethylsiloxane) composites.
This work explores the use of conformal nanoscale plasma coatings on the surface of boron nitride (BN) powders to control the rheological properties of BN/poly(dimethylsiloxane) (PDMS) composites. BN particles are conformally coated with hexafluoropropylene oxide (HFPO) in a tumbling RF-plasma reactor. Following the HFPO plasma treatment, XPS evidence indicates the presence of thin coating on the surface of the particles having a F:C ratio of 1.77. Filled BN/PDMS composites are investigated using oscillatory shear rheometry in the concentration range of 0.09-0.41 vol% (varphi). The addition of the plasma treated BN particles to the PDMS matrix reduces the complex viscosity by 40-60% when compared with equally loaded control samples across a broad concentration range. The frequency dependence of the maximum packing fraction (varphi(m)=0.38-0.42) is also observed for both treated and untreated particles. The maximum packing fraction does not appear to be significantly affected by the conformal plasma polymer treatment. The investigation has shown that the relative dynamic viscosity of the BN/PDMS can be described by the modified Mooney equation.
Boron Compounds↗
Self-organization of amphiphilic polymer in vesicle bilayers composed of surfactant mixtures.
Cryogenic transmission electron microscopy (cryo-TEM) and small angle neutron scattering (SANS) are used to investigate the association of amphiphilic polymers consisting of a double-chain hydrophobic tail attached onto poly(ethylene glycol) (PEG) polymer chains into two different systems of equilibrium vesicles. For cetyltrimethylammonium bromide (CTAB)/sodium perfluorohexanoate (FC(5)) vesicle bilayers, the size distribution of the vesicles slightly becomes narrow in the presence of the polymers, suggesting that the wedge-shaped polymers increase the spontaneous curvature of the vesicles. In contrast, the confinement of polymer molecules inside the CTAB/sodium perfluorooctanoate (FC(7)) vesicles that are stabilized by spontaneous curvature causes an abrupt decrease in the bilayer rigidity. By an analysis of vesicle size distribution, it is found that the membrane elasticity of CTAB/FC(7) vesicles is varied considerably from 6k(B)T to 0.3k(B)T, implying the transition of stabilization mechanism from spontaneous curvature to thermal fluctuation in the presence of polymer. The polymer incorporation mechanism into the bilayers is understood, in the comparison of the vesicle radius and size distribution before and after adding polymer, as that the polymer is anchored into the vesicle bilayer owing to hydrophobic property after the adsorption on the surface of the bilayer.
Caproates↗
Effect of fluorinated groups on photooxidative stability of polymeric protectives applied on marble.
Some new protective copolymers and a commercial one have been tested on Candoglia marble, a very low porosity stone. Two of the polymers contained a partially fluorinated methacrylic monomer, 2,2,2 trifluoro ethyl methacrylate (TFEMA), in combination with either an acrylic, methyl acrylate (MA) or a vinyl ether, n-butyl vinyl ether (n-BVE) unit. Two copolymers, ethyl methacrylate/n-butyl vinyl ether and ethyl methacrylate (EMA)/methyl acrylate (Paraloid B72), were non-fluorinated and similar in compositions and molar ratio. The aim of the work is to test the copolymers and compare the performances of fluorinated new polymers with the non fluorinated one and with the largely used commercial product. The results obtained demonstrate that the introduction, even in limited amounts, of fluorine atoms in the side ester groups of methacrylic type polymers really improves their protective effect and the durability of the stone treatments. The best results were obtained with the copolymer TFEM/MA which is the fluorinated homologous of Paraloid B72.
Acrylates↗
[Polymer fume fever[].
Polymer fume fever is a self-limiting condition with influenza-like symptoms (fever, headache, dry cough, dyspnoea and myalgia). It is caused by inhalation of toxic products released by combustion of fluoro-carbon polymers. There is no causal treatment, and the symptoms usually clear up spontaneously within 24 hours. This article describes an accident where 13 soldiers became ill when exposed to fumes released from a tent oven painted with a coating containing fluoro-carbons.
Adult↗
Electrical phenomena in biorheology.
Electric polarization is important in various subjects in biorheology. Piezoelectricity, that is, stress-induced polarization and electric field-induced strain, is demonstrated in a variety of biological materials including polysaccharides, proteins and deoxyribonucleic acid. Complex piezoelectric constant depends on measuring frequency, temperature and water content. Piezoelectric relaxation is related to microscopic internal strain. Stress-induced potential in bone is produced by shear piezoelectricity in collagen fibers and/or streaming potential in conaliculae. The growth of bone is regulated to best resist external force. The controlling signal seems to be the electric potential. Application of small d.c. current or piezoelectric polymer film stimulates the formation of bone in femur of animals. Various techniques of electrical stimulation are clinically used for healing bone fracture. Pulsing electromagnetic field enhances the proliferation of cell culture.
Animals↗
Continuous wear contact lens surface chemistry and wearability.
Continuous wear (CW) contact lenses are defined as lenses composed of hydrogel polymers containing elements other than carbon, hydrogen, oxygen, and nitrogen that enhance oxygen permeability to an extent greater than water alone. Those elements are silicon and fluorine. Silicon is incorporated as siloxanes, and fluorine is used as fluoroalkyl. Despite the water present in CW lenses, they are not wearable without surface modification because of the tendency of siloxanes and fluoroakyls to move in the soft polymers, orient, and become enriched at the surface. Various methods of surface modification are discussed, with emphasis on the plasma technologies used by the two commercial CW lens products, Focus Night & Day and PureVision. Speculation about future directions in surface chemistry are also presented.
Chemical Phenomena↗
Preliminary in vivo biocompatibility studies on perfluorosulphonic acid polymer membranes for biosensor applications.
The first biocompatibility studies on the DuPont perfluorosulphonic acid polymer (Nafion) are presented. Presterilized samples of commercially cast and solution cast Nafion membranes were implanted subcutaneously, intraperitoneally and intravenously in male Sprague-Dawley rats. Scanning electron microscopy and histological examination of explanted samples and surrounding tissues reveal little, if any, evidence of acute or chronic foreign body inflammatory response. The fibrous capsules surrounding the implant remain nominally thin (less than 100 microns) after more than 3 months in situ, while the surrounding tissue remains well vascularized. Nafion polymer exhibits sufficient biocompatibility to make it a viable candidate for some implantable biosensor applications. It may, however, be necessary to compensate for the effect of the progression of fibrous encapsulation on sensor performance, particularly during the acute response stage.
Abdominal Muscles↗
Surface modification and evaluation of some commonly used catheter materials. I. Surface properties.
Double catheter systems consisting of a stiff outer catheter and a flexible, buoyant, flow-directed, inner catheter which is often balloon-tipped have been employed with increasing frequency recently in both therapeutic and diagnostic procedures. Their use, however, has been restricted because of the excessive friction generated between the two catheters. In an attempt to decrease friction between polymers commonly used as catheter materials, oxidation of polyethylene, fluorinated ethylene-propylene copolymer, poly(vinyl chloride), silicone rubber, and polystyrene surfaces was induced by exposing the polymers to radio frequency glow discharge (RFGD) in a helium environment. All polymers were surface characterized utilizing x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and contact angle measurements before and after oxidation. This article describes the materials and methods used to fabricate and characterize the polymer surfaces and the results of the characterization. The results indicate that increases in oxygen concentration at the surface of the polymers and decreases in air-water contact angles occur with increased RFGD exposure time. Plateau values were usually obtained after 5-30 s exposure time, yet no apparent changes in surface topography were noted by scanning electron microscopy. The hydrophilic surfaces produced were stable for up to three months storage time in air.
Biocompatible Materials↗
Elastomeric fluorinated polyurethane coatings for nontoxic fouling control.
Nontoxic antifouling coatings have been investigated for many years as possible successors to toxic antifouling paints. Polymers containing fluorine or silicone have been tested and each has been shown to be partially effective for different reasons. This paper describes a new coating which combines the best features of fluorinated and silicone coatings and is non-toxic. Four fluorinated elastomers were prepared and tested for fouling resistance during a full fouling season. The surface energy and mechanical properties of each polymer were measured and correlated to fouling performance. One of the elastomers was shown to foul slowly, clean easily, be durable in the marine environment and organisms bonded to it only weakly. The surface energy, elastic modulus, and thickness of the elastomer may be varied as desired over wide ranges to meet differing performance requirements.
Adhesiveness↗
A key factor in modern protection of historic buildings: the assessment of penetration of water-repellent polymers into porous stone-materials.
From the 1960s on, the conservation of monuments and stone masonry has witnessed an increasing use of polymeric products during restoration interventions. Actual penetration depths reached by different polymers within the porous stone matrix are supposed to be key factors in determining the efficacy of the treatments themselves (besides, of course, the chemical-mineralogical nature of the stone and the chemical-physical characteristics of the various polymers). This work presents some preliminary results obtained on specimens of Noto calcarenite treated with various polymeric protective products. Samples were investigated with direct analytical methods (micro-ATR spectroscopy, SEM) in order to assess penetration depths reached by polymers inside the stone while reducing to a minimum the necessary manipulation of specimens. The obtained results highlighted the following trend in penetration depths for the various products tested: siloxane product > partially fluorinated acrylic resin > acrylic resin. Moreover, data obtained allowed to establish direct correlation between long term efficacy of products and relative penetration depths.
Acrylates↗
Nafion-coated electrodes with high selectivity for CNS electrochemistry.
A major improvement in the selectivity of small graphite electrodes used for in vivo electrochemistry is described. The electrodes are coated with Nafion, a perfluorosulfonated polymer. This coating is practically impermeable to ascorbic acid and anionic biogenic amine metabolites and only slightly responsive to neutral metabolites. Thus it becomes selective for the cationic primary neurotransmitters, dopamine, norepinephrine and 5-hydroxytryptamine. Responses of Nafion-coated and untreated electrodes in vivo are compared.
Animals↗
The glass polyphosphonate cement: a novel glass-ionomer cement based on poly(vinyl phosphonic acid).
This paper outlines research which aimed to develop a new type of Glass-ionomer cement, the glass polyphosphonate cement. The glass polyalkenoate cement, a form of Glass-ionomer cement, is now widely used in dentistry and is based on the reaction between an ion-leachable aluminosilicate glass and an aqueous solution of poly(acrylic acid) or its copolymers. The new cements described in this paper employ a novel polymer, poly(vinyl phosphonic acid), PVPA, as the acidic component. This is a much stronger acid than those used in the glass polyalkenoate cement, and various means must be employed to moderate the reaction in order to obtain a viable cement. These cements show a number of important differences in performance in comparison with PAA-based systems and these differences are discussed in the paper.
Fluorocarbon Polymers↗