Showing papers on "Surface modification published in 1990"

Electrochemical Bonding of Amines to Carbon Fiber Surfaces Toward Improved Carbon‐Epoxy Composites

Abstract: Electrochemical oxidation of ω‐diamines on carbon fibers allows the bonding of these molecules to the carbon fibers. The conditions leading to this surface modification are described, and the influence of the different parameters is discussed. The structure of the bonded layer is studied by voltammetry, XPS, and SIMS. A mechanism is proposed which involves the coupling of a radical cation to the fiber. Toughness of carbon‐epoxy composites is improved when prepared from these modified fibers.

Progress in Biomedical Polymers

Abstract: Ophthalmic Polymer Applications.- Contact Lens Materials: Their Properties and Chemistries.- Characterization of Contact Lens Plastics.- Contact Lens Manufacture and Function: Material Related Issues.- Low Voltage Scanning Electron Microscopy (LVSEM) for Improved Surface Characterization of Ocular Implants and Other Prosthetic Devices.- Evaluation of the Tissue-Protective Properties of Hydrophilic Surface Modified Intraocular Lens Implants.- Development of a New Type of Artificial Cornea for Treatment of Endstage Corneal Diseases.- Surgical, Dental and Diagnostic Applications.- Methacrylate Oligomers with Pendant Isocyanate Groups as Tissue Adhesives.- Physical Modification of ?-Cyanoacrylate for Application as Surgical Adhesives.- A Polymeric Bone Replacement Material in Human Oral and Maxillofacial Surgery.- Ceramic Bone Composite Graft for Reconstruction of the Bony Defects of the Maxilla.- Evaluation of Collagen-Immobilized Percutaneous Implants.- Electrophysiological Study of Recovery of Peripheral Nerves Regenerated by a Collagen-Glycosaminoglycan Copolymer Matrix.- Synthesis and Properties of a Polyfluorinated Prepolymer Multifunctional Urethane Methacrylate.- Evaluation of Spiro Orthocarbonate Monomers Capable of Polymerization with Expansion as Ingredients in Dental Composite Materials.- Applications of the Weibull Method of Statistical Analysis of Strength Parameters of Dental Materials.- Polymer and Stability Considerations in Dry Reagent Diagnostic Chemistry.- Quantification of Steroids via a Polymer Linked Second Antibody Enzyme Immunoassay System: Methods of Linking Anti-Rabbit IgG to Poly(styrene).- Polymeric Biomaterials.- The Poly(nonapeptide) of Elastin: A New Elastomeric Polypeptide Biomaterial.- New Transparent and Low-Tensile Set Biocompatible Thermoplastic Elastomers: Poly(siloxane) Modified Poly(olefin) Block Copolymers.- The Poly(urethane) - Calcium Ion Interaction. I. Effect on the Mechanical and Thermal Properties.- Surface Modification of Poly(ether urethane) by Chemical Infusion and Graft Polymerization.- Plasma Techniques for Production of Permanent Hydrophilic Polymer Surfaces for Biomedical Applications.- Influence of Aqueous Environment on Surface Molecular Mobility and Surface Microphase Separated Structure of Segmented Poly(ether urethanes) and Segmented Poly(ether urethane ureas).- In Vitro Analysis of Plasma Protein Diffusion in Crosslinked Gelatin Coatings Used for Blood Pumps.- Development of Absorbable, Ultra High Strength Poly(lactides).- Biodegradable Polyamides Based on 4,4?-Spirobibutyrolactone.- Comparison of Bioabsorbable Poly(ester-amide) Monomers and Polymers In Vivo Using Radiolabeled Homologs.- Chitosan: A Biocompatible Material for Oral and Intravenous Administrations.- Synthetic Poly(phosphates) Related to Nucleic and Teichoic Acids.- Effect of Modification of Poly(vinyl alcohol) Hydrogels on Mouse Fibroblast Cell Growth in Culture.- Medical Applications for Extraction Resistant PVC Compounds.- Controlled Release and Bioactive Polymer Applications.- The Controlled Release of 5-Fluorouracil from Annealed Monolithic Systems.- Monomers and Polymers from Nalidixic Acid - Synthesis, Characterization and Hydrolysis Study.- Antibiotic-Containing Polyurethanes for the Prevention of Foreign-Body Infections.- The Ability of Norgestomet Impregnated Poly(dimethylsiloxane) Implants to Maintain Pregnancy Subsequent to Ovariectomy.- Biological Characterization of Selected Palladium (II) Poly(amides), Poly(thioamides) and Poly(hydrazides).- Platinum II Polyamines: Relationship of Chain Length to Biological Activity.- Contributors.

Surface modification and characterization of particulate mineral fillers

Abstract: The efficacy of the surface treatment of particulate fillers depends on the chemical character of the components, on the method and conditions of the treatment, and on the amount of treating agent. To achieve maximum efficacy the coupling agent must be chosen specifically for each polymer/filler pair. Because of its ionic character CaCO3 can be effectively treated with stearic acid, which forms a basic salt on the filler surface. One stearic acid molecule is attached to each Ca2+ ion and in the complete monolayer the molecules are vertically oriented to the surface. Maximum efficacy is expected at the monomolecular coverage of the surface, but the methods utilized to determine this concentration yielded different results. Stearic acid surface treatment of CaCO3 decreases its surface tension and the effect is more pronounced on the polar than on the dispersion component. The change in the surface characteristics of the filler influences also the properties of the composites in which they are used.

Surface modification of PMDA-oxydianiline polyimide. Surface structure-adhesion relationship

Abstract: Le traitement du pyramellitimide-oxydianiline par la potasse ou la soude aqueuse donne le poly(acide amique) en surface. La profondeur de modification peut etre mesuree par ellipsometrie et ERIR. La modification de surface ameliore fortement l'adhesivite polyimide-polyimide

Estimation of the distribution of surface hydroxyl groups on silica gel, using chemical modification with trichlorosilane

Abstract: An estimate of the relative distribution of the free and bridged surface hydroxyl groups is made, using a surface modification with trichlorosilane according to the following main reaction Si—OH + HSiCl3→Si—O—SiHCl2+ HCl. The amount of chemisorbed chloride groups on the substrates is compared with data on the total amount of surface hydroxyl groups and with hydroxyl group information derived from infrared spectra. The interpretation of these data gives an indication of the reactivity, distribution and concentration of the different types of hydroxyl groups on the surface of silica gel.Trichlorosilane reacts mainly with bridged hydroxyl groups on silica gel, pretreated at low temperatures and exclusively with free hydroxyls at high pretreatment temperatures.Extrapolation of the reactivity of trichlorosilane towards the surface hydroxyl groups demonstrates that bridged hydroxyl groups are present up to pretretment temperatures of 973 K.

Functionalization of colloidal silica and silica surfaces via silylation reactions

Abstract: A series of trialkoxysilane compounds tipped with primary amine groups were used to functionalize the surfaces of glass and colloidal silica. Streaming potential and microelectrophoretic mobility measurements were used to monitor the stability of the functionalized surfaces. Hydrolytic breakdown of the surface-to-silane coupling was induced by either successively increasing and decreasing the pH of the solution in contact with the surface, or by aging the derivatised surfaces in aqueous solution over prolonged periods of time. The chemistry of the spacer units between the trialkoxysilane group and the primary amine tip had a major influence on the subsequent hydrolytic stability. Large hydrophobic spacer groups showed small changes in the electrokinetic properties on storage, but large changes when successively titrated with acid and base through the pH range. The behavior observed with small hydrophobic spacer groups was that large changes in electrokinetic properties were obtained on storage and with pH titration.

Excimer Laser-Induced Surface Activation of Aln for Electroless Metal Deposition

Abstract: A new method for selective metal deposition on aluminum nitride (AIN) is presented. Excimer laser radiation is used for local decomposition of AIN in air. The degree of the surface modification depends on the fluence and number of pulses. A distinct wavelength dependence of the threshold fluence decomposition of AIN was found. The irradiated surface regions act as catalysts in conventional electroless metal plating baths. Structured metal coatings of various elements (Cu, Ni, Au, Pd, etc.) on AIN can thus be obtained in a simple way.

Surface modification of polystyrene by gamma-radiation

Abstract: The effect of gamma-radiation on the surface chemical properties of polystyrene was studied by ESCA and FT-IR Gamma-radiation produces surface >C=O and C-O containing functional groups only, and also causes oxidation to depths > 10 nm as detected by ESCA FT-IR spectra showed that below the top few molecular layers ester, acid, and carbonyl groups of various types were present The α,β-unsaturated carbonyl/acid groups form a higher proportion of the total carbonyls with increasing depth Surface oxidation follows pseudo-first-order kinetics; the extent of interior oxidation is linear with dose

Monomeric surfactants for surface modification of polymers

Abstract: Etude comparative du traitement de surface d'un film de PMMA et d'une laque acrylique photopolymerisable par UV par des agents de surface polymerisables et un polyacrylate agent de surface. Comparaison de la structure des films modifies avec celle de couches monomoleculaires Langmuir-Blodgett des agents de surface polymerisables

Surface modification of biomaterials through noble metal ion implantation.

Abstract: Studies are described involving effects of noble-metal ion implantation on corrosion inhibition and charge-injection capabilities of surgical Ti-6Al-4V alloy. A major factor linked to excellent long-term biological performance is resistance to metal-ion release to tissues. The elements most resistant to corrosion in aqueous solutions are the noble metals. Disadvantages include expense and general inadequacy of mechanical properties. However, if small quantities can be used to surface-modify a surgical device in the last stage of manufacture, that device could possess an optimum combination of environmental integrity, biological response, mechanical properties, and charge-injection capability at miniumum expense. Results for ion-implanted Ir are presented. Iridium has been described as the most corrosion-resistant element known, and its activated oxide as having the highest charge-injection capability of any material known. Ti-6Al-4V samples, ion implanted with 2.5 and 5.0 atomic % peak-maximum concentrations of Ir, were subjected to corrosion treatments to enrich the surface with Ir. Corrosion potential and cyclic voltammetry measurements indicated enrichment in H2SO4, and continued enrichment in isotonic saline, with corrosion potentials approaching that of pure Ir, and charge densities in isotonic saline exceeding that of pure Ir for the 5.0% peak-max Ir implanted material. X-ray photoelectron spectroscopy confirmed the high levels of Ir surface enrichment.

Surface modification of poly(tetrafluoroethylene-co-hexafluoropropylene): introduction of alcohol functionality

Abstract: The reduction of poly(tetrafluoroethylene-co-hexafluoropropylene) was studied with regard to the kinetics of reaction and the product structure. The thickness of the resulting modified surface layer can be controlled by using reaction time and temperature. Hydroboration followed by oxidation introduces alcohol functionality to the surfaces. The reactivity of alcools in esterification reactions is investigated and enhanced. Lower yields of primary alcohols can be directly introduced to the surface by reaction of the reduced layer with 9-BBN, followed by carbonylation and reduction

Surface modification of plastic substrates

Abstract: The present invention is a process for treating plastic substrates to improve their surface properties. The process involves exposing the plastic substrate to UV radiation at wavelengths of 185 and 254 nm in the presence of atomic oxygen for about 5 to 60 minutes. The treated plastic substrates have improved wettability. The process is particularly well suited for the treatment of plastic intraocular lenses and plastic packaging materials such as PVC film.

Kinetics of (CO)polymerizations at the surface of inorganic submicron particles in emulsion-like systems

Abstract: Hydrophilic TiO2 particles were modified with two different titanates and thus made hydrophobic. “Emulsion” polymerizations were carried out in aqueous dispersions of these particles, stabilized with an anionic surfactant. Polymerization kinetics were determined using a densitometer. The effect of several parameters, like surface modification, surfactant and initiator concentration, and stirring speed on polymerizations were studied. Depending on reaction conditions two competitive polymerizations can take place: one in which polymer is formed at the particle surface and one in which free polymer particles are formed. The TiO2 was modified with a titanate containing a methacrylic acid ester, which was used as a comonomer. Thus a chemical bond between TiO2 particles and polymer was obtained. These polymer encapsulated inorganic particles may offer interesting perspectives in those cases, where a good coupling between particles and matrix is important, for instance in latex paints and in polymer composites.

A surface charging technique in photoemission spectroscopic studies of dielectric‐semiconductor structures

Abstract: A surface charging technique used in conjunction with x‐ray photoelectron spectroscopy (XPS) has been applied as an in situ surface analytical tool for the studies of the fabrication of dielectric‐semiconductor structures. It was found that the measurements of surface composition and Fermi level position by XPS gives useful information on the effects of in situ surface modification prior to the deposition of the dielectric film and on the properties of the dielectric‐semiconductor structure. When the thin dielectric film thickness is within 10 nm, XPS yields information on both the dielectric film and the semiconductor at the interface, and thereby allows the monitoring of the initial growth of the dielectric film. In addition to this conventional approach, surface charging of the thin dielectric film during XPS analysis, either by photoemission or by flooding the surface with low‐energy electrons, provides additional information on Fermi level stabilization of the semiconductor at the insulator‐semicondu...

DMA and ATR FT‐IR studies of gas plasma modified silicone elastomer surfaces

Abstract: The results obtained from ATR FT-IR and DMA studies of gas/plasma surface modified silicone elastomers are presented. The structural analysis indicates that, upon the plasma treatment in the presence of argon and carbon dioxide gases, the primary components of the surface are short chain layers with carbonyl groups. Their presence significantly influences the viscoelastic properties of the elastomer. The measurements of the storage modulus (E′) indicate a substantial decrease of the crosslink density upon the plasma treatment. Although the glass transition temperature also changes, these changes do not follow the trend observed of E′ values, and primarily depend on the chemical structures that develop upon the treatment. On the other hand, the ammonia–plasma surface modification introduces surface amide groups on the surface of the silicone elastomer, which effectively contribute to the increase of both Tg and storage modulus of the elastomer.

Some properties of polyethylene compounds with surface‐modified fillers

Abstract: The dispersion of variously surface-treated CaCo3 fillers in linear low density polyethylene has been studied, along with mechanical properties of the filled compounds. Microwave plasma discharges were used to modify the filler surfaces. Inverse gas chromatographic analyses showed that plasma treatments could change the dispersive and non-dispersive components of filler surface characteristics. A reduction in these surface energies facilitated the dispersion of the filler in the non-polar polyethylene. Mechanical properties, particularly those at high deformation of the filled plastic, also responded to filler surface treatments, the ductility at failure increasing with a decrease in the filler's surface polarity. For any given elongation at failure, it was found that the amount of filler accommodated by the host polymer was raised by the appropriate surface modification procedure. The work illustrates the important contribution made by interfacial phenomena to various performance aspects of complex polymer systems.

The infiltration of aluminum into silicon carbide compacts

Abstract: Although liquid-metal processing of metal matrix composites offers economic advantages, problems related to the nonwetting nature of the ceramic discontinuous reinforcement create obstacles to its ready implementation. Infiltration can occur only if a threshold pressure is applied to overcome the unfavorable interfacial forces in the system. The research reported in this paper has been devoted primarily to experiments on infiltrating silicon carbide compacts with pure aluminum, aluminum-1 wt pet magnesium, and aluminum-1 wt pet silicon. The major finding has been that an incubation time is necessary before infiltration can proceed, even though the threshold pressure is exceeded. Thus, while the model equations available for predicting the infiltration rate of compacts appear to be adequate, the incubation time can represent the rate-determining step in the process. It is suggested that the mechanism responsible for the incubation phenomenon may be related to a surface modification produced by either reaction of liquid aluminum with an oxide film on the surface of the particles or coverage of the surface by a capillarity-induced aluminum condensate.

Hydrophilic surface modification of polyethylene by NO-plasma treatment

Abstract: The surface modification of polyethylene surfaces by NO-plasma irradiation was investigated from the point of view of the hydrophilicity and chemical composition. The hydrophilicity was evaluated from the advancing contact angle of water and the surface energy. The chemical composition of the modified surfaces was determined by diffuse reflectance Fourier transform infrared spectroscopy and XPS. NO-plasma irradiation for 5 min made the polyethylene surfaces hydrophilic. The advancing contact angle of water on the modified polyethylene surfaces reached 28 deg, and the surface energy was 57.6 mJ/m2. The incorporation of oxygen and nitrogen moieties on the polyethylene surfaces occurred during the NO-plasma irradiation. The main oxygen moieties were carbonyl groups, hydroxyl groups, and ether linkages; the nitrogen moieties were amino groups. NO-plasma irradiation was more effective in improving the hydrophilicity than the O2 plasma, N2 plasma, or corona discharge treatment.

Stable, covalently-bonded supports for chemical separation apparatus made through a hydride intermediate

Abstract: The present invention produces very stable, covalently bonded separation substrates for separations application such as liquid and gas chromatography as well as capillary zone electrophoresis. An intermediate substrate is prepared which has hydride species on the substrate surface. These hydrides preferably are further derivatized by the catalytic addition of organic compounds bearing a terminal vinyl group. The final surface modification contains closely packed, direct carbon linkages that are stable.

On the Reaction Kinetics in Laser-Induced Pyrolytic Chemical Processing

Abstract: Reaction rates, particle densities, and temperature distribution in pyrolytic (photothermal) laser-induced microchemical processing are investigated with respect to temperature and concentration-dependent transport coefficients, and with respect to the effect of thermal diffusion. While the model employed is particularly suitable for laser-induced chemical vapor deposition (LCVD), it can also be applied to many cases of laser-induced surface modification and dry-etching.

The enhanced attachment and growth of endothelial cells on anhydrous ammonia gaseous plasma modified surfaces of polystyrene and poly(tetrafluoroethylene).

Abstract: Anhydrous ammonia gaseous plasma technique was used for the surface modification of polystyrene petri dishes and poly(tetrafluoroethylene) (PTFE) membranes. Amino groups were added onto surfaces by exposing them to ammonia plasma. Plasma modified polymeric surfaces and control polymeric surfaces were seeded with bovine pulmonary artery endothelial cells (EC). It was found that attachment of EC to control polystyrene surface was negligible. On the plasma modified polystyrene surface, there was improved attachment and growth of EC. At 96 hours, plasma modified surfaces yielded an order of 3 magnitudes more cells compared to those on control. Twenty four hours after seeding the cells, the percentage of EC attachment to control PTFE surfaces and modified surfaces were found to be about 36% and 92% respectively.

Coatings and surface modification by methane plasma polymerization

Abstract: Polymers formed from plasma-polymerized methane were employed to modify the surface properties of silicone rubber membrane. Polymers were evaluated based on the energy input parameter W/FM, where W is the discharge power, F is the monomer flow rate, and M is the molecular weight of the monomer. Dealing with the characteristics of plasma polymerization and the deposited polymer film, the effect of pumping rate on deposition rate and the coating thickness, surface energy, and gas permeabilities of methane-plasma-polymer-coated silicone rubber membrane were investigated in three plasma regions. Because more reactive species are expelled at high pumping rates, the monomer-deficient region is reached at lower W/FM in the high pumping rate system than that in the low pumping rate system. The composite parameter W/FM had a strong influence on coating thickness, gas permeability, surface energy, and the polar component of the surface energy but little effect on its dispersion component. Examination of gas permeabilities indicated that coating thickness was another important controlling factor on the properties of plasma polymer.

Novel photoreactive surface modification technology for fabricated devices.

Abstract: A novel surface process technology was developed to improve biocompatibility of fabricated devices, such as artificial blood pumps The developed technology is based on photochemistry of a phenyl azide group, which is capable of covalently binding a synthetic polymer or protein to substrate surfaces upon ultraviolet (UV) irradiation The photoreactive co-polymers or proteins, which were grafted or modified with phenyl azide groups, were successfully chemically fixed to surfaces Photoreactive, hydrophilic copolymers with poly(dimethyl acrylamide) and albumin, both of which were chemically fixed on surfaces, were found effective for blood compatible surfaces; a fibronectin-bound surface was suitable for providing tissue compatibility The quartz optical fiber guided UV irradiation system enables one to provide desired biocompatibility to a specific part of a fabricated device

Acid-base interfaces in fiber-reinforced polymer composites

Abstract: The role of Lewis acid-base interactions at the fiber-matrix interface in composites is studied with both glass and Teflon fibers. In the glass fiber case, surface chemistry is modified with amino-, methacryloxy- and glycidoxy-silane coupling agents (A-1100, A-174 and A-187, respectively). Silane adsorption mechanisms as well as the properties of filament-wound, unidirectional epoxy and polyester composites are explained by a combination of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and flow microcalorimetry. The heats of adsorption of pyridine and phenol prove that the coupling agents add acidic sites to the glass fiber surface as well as stronger basic sites. The subsequent adhesion of the matrix polymers and the short beam shear strengths of composites are explained on this basis. The Teflon fibers are first etched with sodium naphthalene solutions, and then sequentially hydroborated and acetylated, producing approximately monofunctional hydroxyl (acidic) and ester (bas...

Recent developments in the functionalization of latex particles

Abstract: A survey of the recent literature is given concerning the synthesis and characterization of functionalized latex particles. Two main methods have been particularly considered and discussed: first, the functionalization of latexes by copolymerization of a basic monomer with adding small amount of a monomer bearing a chemical reactive group, with a special emphasis on the kinetics, the distribution of the functional monomer, the surface morphology of latex particles and the optimization of processes; secondly, the use of surface-active monomers in such reactions which may confer potential advantages (low level of water-soluble polymers, control of surface charge density) in comparison with the former ones, provided further information can be obtained on their kinetic behavior in emulsion polymerization.