Silica polymer-modified

After milling, and deeper removal where cracking and spalling have occurred, a bridge or car park deck can then patched in the delaminated areas and a dense cementitious overlay of micro silica, polymer modified or low slump, low water/cement ratio concrete or other suitable waterproofing (chloride ingress resistant) deck concrete is put back on. This will slow the corrosion rate and the appearance of further delaminations (Figure 5.10). 

Portland cement is susceptible to corrosion by CO2 and H2S. The chemical attack by CO2 is called carbonation. A microsample technique has been developed to study the CO2 corrosion in cements, because the corrosion is difficult to monitor with common test procedures [264]. This technique is also advantageous as an accelerated testing method. A polymer-modified cement has been tested in field studies [694]. The addition of silica also improves chemical resistance [146], in particular brine corrosion. 

If the hydrolyses in organosilicate-polymer systems are carried out with increased amounts of the silicate, bicontinuous phases can be obtained (with the silica and polymer phases interpenetrating one another) [213]. At still-higher concentrations of the silicate, the silica generated becomes the continuous phase, with the polymer dispersed in it. The result is a polymer-modified ceramic, variously called an "ORMOCER" [214,215], "CERAMER" [216,217], or "POLY-CERAM" [218,219]. It is obviously of considerable importance to determine how the elastomeric phase modifies the ceramic in which it is dispersed. 

Plasma Polymerization. Plasma-induced polymerization (24) of vinyl monomer from inorganic particles is also employed for polymer grafting. The conventional reactors for liquid-phase polymerization of vinyl compounds after generation of plasma on inorganic particles or powders have been recently invented by Ikeda et al. (25). Haraguchi et al. (26) have also prepared polymer-modified silica by plasma-induced polymerization of glycidyl methaciylate. 

If the hydrolyses in silane precursor-polymer systems are carried out using relatively large amounts of the silane, then the silica generated can become the continuous phase, with the elastomeric polysiloxane dispersed in it.12 14 136-143 Again, a variety of ceramic components and polymeric components have been studied. The resultant composite is a polymer-modified glass or ceramic, frequently of very good transparency. Although its thermal stability will be inferior to that of the ceramic component itself, there are many applications for ceramic-type materials where this is not a serious problem. 

Several thermoresponsive polymer coatings have been applied in the chromatographic separation of biomolecules. The group of Okano has been active in the field for some time. In recent work, silica beads modified with PNIPAM brushes prepared... 

The reaction with C02, as reported for the dried aminosilane polymer also occurs with immobilized aminosilane molecules. Culler43 reported that approximately half of the amine groups are reacting with C02 when silica samples modified with APTS in aqueous solution, are dried in air. Comparison with AEAPTS and a triaminosilane showed that only primary amines react with C02. The reaction product is evidenced by FTIR bands at 1630, 1575, 1488 and 1332 cm 1. Also after modification in dry conditions and drying at room temperature in humid air, the reaction with C02 may be observed. Characteristic infrared bands appear upon modification at high concentrations of APTS. Figure 9.32 shows the infrared spectrum of dry silica, modified with a 10% APTS/toluene solution, after air drying for 30 minutes. 

The choice of the sorbent is dictated by the characteristics of both the analytes and their potential interferences. The sorbents most frequently employed here are silica, alkylsilane-modified silica (bonded phases), alumina, porous polymers (with and without ion-exchange groups) and carbon-based materials. One typical application is a method for the determination of hexavalent chromium in soils [10] using the on-line system depicted in Fig. 4.9. After USAL, the analytes in the leachate were directly determined or preconcentrated depending on their concentration. Concentration was performed by on-line solid-phase extraction using a laboratory-made minicolumn packed with a strong anion-exchange resin. The absolute limits of detection were 4.52 and 1.23 ng without and with preconcentration, respectively. 

Other oiganic—inoiganic hybrids include poly(eth5ioxazoline)—silica, poly(vinyl alcohol)—silica, poly(arylene ether) ketone—silica, polyimide—silica, polyozoline—silica, poly(eth5iene oxide)—silica, and polymers—modified alkoxysilane. 

Spin-coated PS/PMMA films were used as samples to study silica-polymer interactions. For this purpose, solutions of 10 mg polymer in 1 mL toluene were prepared flom each polymer. The PMMA and PS solutions were mixed in a ratio of 2 1. When the mixed solution was spin-coated on a fleshly cleaned silicon surface a phase-separated film of 100 nm thickness was obtained. Cantilevers were modified either by deposition in the saturated atmosphere of hexamethyldisilizane or immersion in a 2% solution of dimethyldichlorosilane in toluene. Typically, measuring the contact angle of the sample after modification gives proof of hydrophobization. However, because of the small size of the tips the contact angle cannot be estimated. Thus, at the same time as the cantilever modification, small pieces of silicon wafers were modified to enable contact angle measurements to be made. 

Organic polymer layer on the surface of silica gels or porous silica can modify the surface to increase the resistance of the silica surface to basic compounds. 

Basically, one can distinguish three kinds of CSPs, chiral polymers (Type 1), achiral matrices (mainly silica gel) modified with chiral moieties (Type 11), and imprinted materials (Fig. 6.3). 

Solid-liquid extraction by use of sorbents (silica, alkyIsllane-modified silica, alumina, porous polymers with or without ion-exchange groups or carbon materials) contained in a cartridge or a short stainless-steel or glass column is the pretreatment most commonly used at present for some types of samples... 

Traditionally, low crosslinked porous polymers modified by sulfonic or carboxylic acid groups (quaternary amines for the separation of cations) were the most widely used stationary phases. In recent years, silica-based chemically bonded or surface-modified (e.g. alumina treated) ion exchangers have found increasing use [159,484-488]. The trend towards increased use of modern porous polymer and silica-based materials is due to their higher performance and greater dimensional stability with different mobile phase compositions. 

The amount of Si ions dissolution is found to be dependent on surface modification, which was confirmed by induchvely coupled plasma-atomic emission spectrometer (ICP-AES) analysis. Table 2.2 shows the dissolution amount of Si ions with and without surface modification of fumed silica slurry. Without surface modification, the amount of Si dissoluhon was 1.370 0.002 mol/L, whereas surfaces modified with poly(vinylpyrrolidone) (PVP) polymer yielded a dissoluhon of 0.070 0.001 mol/L, almost 20 hmes less than the unmodified surface. Figure 2.6 represents the electro-kinetic behavior of silica characterized by electrosonic amplitude (ESA) with and without surface modification. When PVP polymer modified the silica surface, d5mamic mobility of silica particles showed a reduchon from -9 to -7 mobility units (10 m /Vxs). Dynamic mobility of silica particles lacking this passivation layer shows that silica suspensions exhibit negative surface potentials at pH values above 3.5, and reach a maximum potential at pH 9.0. However, beyond pH 9.0, the electrokinetic potential decreases with an increasing suspension pH. This effect is attributed to a compression of the electrical double layer due to the dissolution of Si ions, which resulted in an increase of ionic silicate species in solution and the presence of alkali ionic species. When the silica surface was modified by... 

Independent of our work, Mosbach et al. (78) prepared cavities in chin polymer layers on the surface of silica. They used certain dyes for imprinting. The polymer-modified silicas were used also for HPLC investigations. 

Usually the silica/polymer composites are prepared with styrene, MMA, BA, or their copolymers. However, few reports cover experiments with less commonly used polymers such as poly(styrene sulfonic acid) (PSSA), poly(hydroxyethylmethacry-late) (PHFMA), poly(aminoethylmethacrylate) PAEMA [133], polyethylene (PE) [134], or polyamides [135]. Using a miniemulsion of nickel-based catalysts for the polymerization of ethylene, which is dispersed in toluene in the presence of hy-drophobically modified silica particles, PEysilica hybrids could be prepared [134]. The ethylene is introduced into the system by bubbling through the miniemulsion. The hydrophobic moiety of the silica particles interacts with the growing polymer and leads to lentil-shaped or isotropic hybrids. Lentil-shaped particles are composed of semicrystalline PE, whereas the isotropic hybrids are composed of amorphous polymer. The crystallinity of the polymer is determined by the choice of polymerization catalyst. Silica/polyamide hybrid nanoparticles were prepared with 3-aminopropyltriethoxysilane (APS)-modified silica particles [135]. These particles were dispersed in sebacoylchloride and the solution miniemulsifled in an aqueous... 

In the first approach, prolinamides have been supported on micelleforming species, dendrimers (32a-c), polystyrene (26, 31a-d), poly-vinylidene chloride, phenolic polymers, ionic liquids, silica (28, 29), other inorganic supports (30), ° and polymer-modified small peptides. Supported prolinamide catalysts have also been prepared by acrylic and styrene (27) copolymerisation. 

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