The effect of surface treatments of glass capillaries on column performance

Summary The effects of etching and/or silylation of glass capillaries on column efficiency were studied. Coated with apolar OV-101, only columns subjected to the combined treatment showed an increase of about 50% in the number of effective plates. Surface hydroxylation, prior to silylation, gave a small additional improvement for this stationary phase.     

Novel organosilicon dendrons as effective linkers for biomolecules binding on a glass surface

A new, flexible and selective protocol for the synthesis of new organofunctional silicon dendrons of the general formula EtOSi(CH₂CH₂SiMe₂CH₂CH₂SiMe₂R)₃ (where R is an amine or epoxy substituent) has been developed. The title compounds have been efficiently obtained via Karstedt platinum‐catalysed hydrosilylation and linked to a glass surface. Modified solid supports are successfully applied in immobilization of proteins, especially monoclonal antibodies against a wide range of antigens. Copyright © 2015 John Wiley & Sons, Ltd.     

Adhesive composite materials based on glass and carbon fillers

Grades and physicomechanical characteristics of glass and carbon fiber-reinforced plastics based on adhesive prepregs are presented. Certain fields of application of these materials are shown.     

Effect of glass fiber surface treatments on mechanical strength of epoxy based composite materials

Sizing glass fibers with silane coupling agents enhances the adhesion and the durability of the fiber/polymer matrix interface in composite materials. There are several tests to determine the interfacial strength between a fiber and resin, but all of them present difficulties in interpreting the results and/or sample preparation. In this study, we observed the influence of different aminosilanes fiber coatings on the resistance of epoxy-based composite materials using a very easy fractographic test. In addition, we tried a new fluorescence method to get information on a molecular level precisely at the interface. Strength was taken into account from two standpoints: (i) mechanical strength and (ii) the resistance to hydrolysis of the interface in oriented glass-reinforced epoxy-based composites. Three silanes: gamma-aminopropyltriethoxysilane, gamma-Aminopropylmethyldiethoxysilane, and gamma-Aminopropyldimethylethoxysilane were used to obtain different molecular structures at the interface. It was concluded that: (i) the more accessible amine groups are, the higher the interface rigidity is; (ii) an interpenetrating network mechanism seems to be the most important for adhesion and therefore to the interfacial strength; and (iii) the higher the degree of crosslinking in the silane coupling layer is, the higher the hydrolytic damage rate is.     

NIR studies of the surface modification in silica fillers

Methods of estimating the degree of condensation of the surface silanol groups of silica due to its modification by silane coupling agents are reported.Also, a procedure for estimating the surface silanol groups for the pre- and post-modified silicas for the NIR 7326 cm^–1 band is given.Using electron microscope studies and heats of immersion of silica surfaces, the silane effect on agglomeration of silica particles and, thus, on the physicochemical properties of its surface has been demonstrated.     

Novel alkali-niobic bismuth germanate glass system

Journal of Thermal Analysis and Calorimetry - Equimolar Nb2O5:Li2O co-doped BGO70 (Bi2O3:GeO2 = 30:70) glasses were prepared via melt–quench method. Their XRD pattern and...     

Characterisation of the surface structure and bioactivity of glass and glass ceramics using surface topography

The present paper reports the results of the relationship between the surface topography, microstructure and the in vitro bioactivity of samples with and without fluorapatite content in simulated body fluid. Glasses and glass ceramics belonging to the Li₂O-SiO₂-CaO-P₂O₅-CaF₂ system were prepared by using conventional melting technique following by heat treatment to obtain glass ceramics. This current study demonstrates the benefits of combining two microscopic methods for better investigation of the surface structure. The formation of apatite layer on the surface and the increase in surface roughness proved that the glasses and glass ceramics with bioactive fluorapatite content could satisfy to the requirements for biomaterial applications. The results also showed that the roughness of apatite layer formed after immersion in body fluid on the surface of glasses with fluorapatite was more pronounced than that of equivalent glass ceramic samples cured under the same conditions.      

Characterization of surface interaction of inorganic fillers with silane coupling agents

Coupling agent (CA) can not only help filler achieve better dispersion in polymer matrix, but also improve the roughness of the composite with good rigidity at the same time. In this paper, the interaction of silane coupling agents with inorganic fillers (in our case are Mg(OH)₂ and CaCO₃) were studied by pyrolysis gas chromatography (PGC), as well as Fourier transform infrared spectroscopy. By two-step pyrolysis (first at 250 °C, then at 600 °C), physisorbed and chemisorbed silane on fillers can be distinguished. The bonded silane cannot be flash vaporized at 250 °C, it results in new peaks different from that of silane in pyrograms at 600 °C. The chemisorbed amount of silane increases with time and temperature and finally reaches a plateau. The result showed that PGC was an effective analytical tool to prove the existence of interaction between inorganic filler and CA.     

Laser surface treatments for adhesion improvement of aluminium alloys structural joints

Laser technology is proposed as a friendly alternative treatment to chemicals involved in conventional prebonding adherend treatments. Aluminium alloy 2024 substrates were laser treated with different beam diameters and energy densities, and bonded using a structural epoxy adhesive. The influence of irradiation conditions on adherends morphology and adhesive joints’ fracture energy was investigated. On the basis of different morphologies observed, an explanation of the effect of the surface treatment upon joint mechanical behaviour is attempted.     

Thermal analysis of the polymerization process on the surface of inorganic fillers

The thermal polymerization of pentabromobenzyl (mono)acrylate (PBB-MA) on the surface of the inorganic fillers Mg(OH)₂ and CaCO₃ was studied. FTIR spectroscopy and extraction of the polymer in bromobenzene show that polypentabromobenzyl acrylate (PBB-PA) was mostly grafted on the surface of Mg(OH)₂. Thermal analysis (TG, DSC, isothermal DSC (IDSC)) demonstrated an increase in polymerization starting temperature, and differences in polymerization enthalpy and apparent activation energy when an inorganic filler is added. These differences depend on the chemical composition of the filler used.The authors acknowledge valuable discussions with Prof. S. Yariv. The authors are also grateful to Berecha Foundation (Geneva) for the financial support of this work.     

Effects of dehydration on the apolar surface energetics of inorganic paper fillers

The surface energies of various inorganic fillers including kaolin clay, titanium dioxide, and talc were examined using inverse gas chromatography (IGC). In an earlier investigation that examined calcium carbonate fillers, dehydration by heating under a dry nitrogen purge had a substantial influence on the apolar (gammaS(LW)) and polar (gammaS(AB)) components of surface energy as measured using IGC. Using the same approach, the influence of such conditioning on several inorganic fillers used in papermaking were determined using preconditioning IGC from 100 to 300 degrees C, and sequential isothermal analysis at 100 degrees C. Results from IGC analysis of titanium dioxides (rutile and anatase) were similar to precipitated calcium carbonate (PCC) for temperatures up to 200 degrees C. PCC was significantly more energetic after preconditioning at 300 degrees C, which may indicate the onset of significant thermal decomposition that titanium dioxides will not exhibit. Kaolin clay samples had relatively high apolar surface energy similar to that of the chalk samples. Calcination gave lower gammaS(LW) values that could not be accounted for by changes in the microporous structure. More likely the differences resulted from contamination of highly energetic surface sites with adsorbates other than water. Talc samples exhibited relatively high apolar surface energies that increased with preconditioning temperature. The results provided insight into the significance of water on the final adhesion properties of fillers in the sheet structure or coating layer.     

Surface treatment of glass-reinforced plastics: Structural study of silane finish layers on the surface of glass fillers. Modification of finishes by transition metal salts

The structure and chemical composition of glass fiber surface treatment substances and their influence on composite materials properties are analyzed.     

Estimation of the surface energetic heterogeneity of fillers by inverse gas chromatography

The surface properties of the fillers are determining for obtaining high performance filled polymers. Yet, their determination is most difficult. This paper proposes to use inverse gas chromatography, either at infinite dilution or finite concentration conditions, to estimate surface energy and nanomorphological characteristics, but also surface heterogeneity of different clays, talcs of various origins and ground muscovites.     

Viscoelastic and surface properties of polymer complexes with fillers of different nature

Rheological and surface properties of polymer blends based on aqueous solutions of polyacryl-amide and polyvinyl alcohol were studied by viscometry and methods of penetration of a spherical indenter and detachment of a metal plate from a polymer body. The work of adhesion was examined in relation to the filler type and the time of formation of the polymer composites.     

A new approach to the design of surface treatments for reinforcing agents

A new approach for design of improved interfacial bonding between carbon fibers and polymeric matrices is described. In this method the affinity of surface-treated carbon fibers to various polymer matrices is simulated by analyzing the adsorption characteristics of model compounds, typical of the polymer units, onto very high surface area carbon fibers. The affinity can be evaluated by the use of Thermogravimetric Analysis (TGA) to measure adsorption–desorption characteristics. Since high surface area, activated carbon fibers (ACF) can be chemically treated to obtain acidic, basic, nonpolar or highly polar surfaces, it should be possible to assess the interactions of chemically modified surfaces with model compounds such as methanol (MeOH), acetone, dimethylformamide (DMF), dimethylether, tetrahydrofuran (THF) and water. Some preliminary results are presented, indicating that surface treatments for carbon fibers other than oxidation may lead to enhanced bonding with polymeric matrices.     

Polymeric cross-linked surface treatments for controlling block copolymer orientation in thin films

The orientation of cylinder-forming poly(styrene-block-methyl methacrylate) [P(S-b-MMA)] was investigated on two sets of polymeric surface treatments: 10 para-substituted polystyrene derivatives with <10 mol % poly(4-vinylbenzyl azide) and a series of poly(styrene-random-4-vinylbenzyl azide) [P(S-r-VBzAz)] copolymers with 5-100 mol % poly(4-vinylbenzyl azide). The copolymers were spin-coated to form thin films and then cross-linked by heating. The resulting films exhibited a range of surface tensions from 21 to 45 dyn/cm. Perpendicular orientation of P(S-b-MMA) cylinders was achieved with poly(p-bromostyrene) and all the [P(S-r-VBzAz)] copolymer surface treatments, most notably the homopolymer of poly(4-vinylbenzyl azide). Films made from these simple copolymers are as effective as random terpolymer alignment layers commonly made from both block monomers and a cross-linkable monomer.     

Effect of post-irradiation thermal treatments on the stability of gamma-irradiated glass dosimeter

A commercial window glass has been investigated as a routine high dose dosimeter for gamma irradiation. The irradiated samples showed rapid fading at room temperature immediately after irradiation. This short-term rapid fading was followed by a slow fading at long-term. This strong initial fading is a problem for dosimetry purposes. However, when the dosimeter is measured at the same time interval after irradiation, it maintains proportionality to dose. Calibration curves have to be used for different time intervals after irradiation. In order to improve post-irradiation stability dosimeters were submitted to different post-irradiation thermal treatments from (−20) up to 150 °C. After that, optical absorbance measurements were carried out up to 2 months at room temperature. The heating at 150 °C for 20 min was found to be the most suitable procedure for the removal of unstable entities responsible for the initial rapid fading. Due to these heat treatments, variation of response was found almost negligible 24 h after irradiation for several months. Calibration curves demonstrated the applicability of this glass as routine dosimeter in the dose range of 0.5–90 kGy.