Silica plasma-coated

In Fig. 23, the bound rubber values are shown of S-SBR/EPDM-blend samples filled with untreated silica, plasma-coated silicas, and silane-modified silica. The plasma-treated silicas show in all cases a significantly higher bound rubber content... 

To improve chromatographic separation, another analytical column could be used in addition to the monolith (Xu et al. 2006). The monolith column served as an extraction column only. Hsieh et al. (2000, 2002) utilized a polymer-coated mixed function (PCMF) Capcell C8 column (4.6 x 50 mm, Phenomenex) to provide dual functions—online plasma extraction and analyte separation. The silica was coated with a polymer containing both hydrophilic polyoxythylene and hydrophobic groups. The diluted plasma samples (1 1 to 1 3) were injected directly. No column deterioration was observed after 200 injections. 

Plasma chemical synthesis, 1 717 Plasma chemical vapor deposition (PCVD), in fiber optic fabrication, 11 139-140 Plasma coatings, 5 665 Plasma deposition, in vitreous silica manufacture, 22 414, 415 Plasma derivatives, 12 129t... 

Surface modification of silica, another filler used in the rubber industry, has been reported by Nah et al. [36, 37]. The silica surface was modified by plasma polymerization of acetylene. The modified silica was mixed with SBR to study its performance. They observed an increase in reinforcement with the plasma-modified silica and hence better mechanical properties. They also observed an improvement in the dispersion properties for the plasma-coated silica. The authors explained the observed improvement in properties by a mild crosslinking between plasma-polymerized acetylene and the butadiene part of the SBR matrix. 

Effect of Plasma-Coated Silica on SBR Compound Properties... 

For silica, the plasma-pyrrole coating clearly improves the compatibihty of the silica in the polymer blend. In contrast to this, the plasma-acetylene and plasma-thiophene treatments cause a high filler-filler interaction. This can be explained by the differences in compatibility between the plasma coatings and the polymers. In the case of PA-silica, the coating results in a higher compatibility towards EPDM in the blend, which could lead to an overconcentration of silica in the EPDM phase, with increased agglomeration of the filler. 

Comparing the three substrates that were plasma-coated in this study, it has become clear that silica is very easy to encapsulate with a plasma coating, whereas carbon black is difficult to treat because of its inert chemical surface structure. Sulfur is also more difficult to handle, but in this case the incomplete coating is an advantage because the sulfur has to be released from the encapsulation shell in order to be efficient as curing agent. In all cases, the polarity of the substrate is reduced. 

Application of a plasma coating onto carbon black is very difficult compared to silica. It was only practically feasible for fullerene soot (left over from the fullerene production), which contains a large amount of reactive groups on its surface. Polyacetylene-plasma-treated fullerene soot provides an improved dispersion in SBR and in a SBR/EPDM blend compared to untreated fullerene black. However, the effect on the stress-strain properties is rather limited and the coating has only a slight effect on the final properties. 

SPME capillary gas chromatography (SPME-GC) can be used for the extraction of organometal compounds after these have been derivatized to a sufficiently volatile form (see also organotin speciation). A silica fiber coated with polydimethylsiloxane (PDMS) is brought into the (headspace) of the sample. After exposure, the fiber is inserted into the GC injection port and the compounds are thermally desorbed for subsequent analysis. This method has higher sensitivity compared to the injection of solvent on a capillary column (usually 1 fil) but requires the use of standard addition as a calibration method. After GC separation, analysis can be performed by furnace atomization plasma emission spectrometry (FARES)." ... 

Gas chromatographic research with plasma-coated silica gel adsorbent and an ultrafiltration test of organic solutes having different molecular sizes have revealed that the polymer appears to have micropores of 2-4 nm in diameter. Control of the dissolution rate of pharmaceuticals by dianging the polymer film thickness was also attempted [72], It was found that propargyl alcohol is a very promising monomer and a few applications of this hydrophilic plasma polymer have been reported [72]. 

In a subsequent paper (42) Justova et al. introduced two important improvements. The TLC step was optimized by replacing conventional silica gel-coated plates by their HPTLC counterparts. Furthermore, the repetitive extraction of the silica gel to recover the compound to be quantitated could be eliminated. It now sufficed to scrape off the adsorbent and wet it with a small volume of solvent to make it directly amenable to the radioligand determination. Thus, by combining the HPTLC step with a simple extraction of deproteinized plasma using toluene, nanogram amounts of 25(OH)D, 24,2S(0H)2D, and 2S,26(OH)2D could be quantitated in 1-ml plasma samples. The same approach based on an identical HPTLC system and a modified radioligand procedure was later applied to the determination of picogram amounts of l,25(OH)2D in plasma (I ml) (43). 

Polar phases are used almost universally for fatty acid analysis, although the inherent resolution of WCOT columns is such that some remarkable separations can be achieved even with non-polar silicone phases, which are more stable at elevated temperatures. Such columns are easier to manufacture than are polar ones. For example, the separation of a hydrogenated fish oil is a horrendous problem for any stationary phase, yet a published chromatogram obtained with a 44 m column coated with the non-polar OV-73 (175,000 theoretical plates) is probably as good as any in which polar phases have been used [870]. A set of retention data has been published for cod liver oil fatty acids on a 50 m fused silica column coated with SP-2100 a large number of isomeric branched-chain monoenoic and polyenoic components were clearly resolved [298]. A short column of this type was used for the analysis of plasma fatty acids [925]. 

For the surface modification of silica and carbon black, a radiofrequency (13.56 MHz) electrode-less tumbler plasma reactor at the University of Cincinnati was used. The schematic reactor design is shown in Fig. 5. It consists of a Pyrex cylinder chamber of 40 cm in length and 20 cm in diameter, with a motor-driven shaft at its center, and two vanes running in opposite directions. The reactor is based on a horizontal mixing principle and is capable of treating 350 g per batch. The powdery materials to be coated are placed at the bottom of the chamber. The plasma... 

Hydrophobicity - Before plasma treatment, silica powder is highly hydrophilic and immediately sinks in water. After plasma film deposition, the material floats on water for several hours. A significant reduction in polarity and in surface energy compared to untreated silica is found, down to the range of 28.4-47.7 mJ/m2. The water penetration into powder beds of untreated and plasma-treated silica is shown in Fig. 7. The untreated silica absorbs water very fast, whereas the plasma-treated silicas show a significantly decreased water penetration rate. The lowest rate is found for the polythiophene-coated silica (PTh-silica). 

Amount of deposited material - The difference in weight loss between coated and untreated silica corresponds to the weight of the plasma-polymerized film deposited on the surface. For the plasma-treated silicas, decomposition of the coating starts at 265°C for poly acetylene, 200°C for polypyrrole, and 225°C for poly thiophene, and is complete at 600°C. Between 265 and 600°C, PA-silica shows 6 wt% weight loss, and PPy- and PTh-silicas show 4.5 wt% and 5 wt% loss, respectively. 

Fig. 7 Water penetration into powder beds of untreated silica and plasma-polymerized acetylene-, pyrrole-, and thiophene-coated silica...

In all the cases of poly acetylene, polythiophene, and polypyrrole coating, the amount of plasma-film deposition was different, caused by the difference in the structure of the three different monomers and their reactivity during the plasma process. PPy- and PTh-silica are more hydrophobic than PA-silica, probably due to the presence of different chemical moieties in the complex film structure deposited onto the silica surface. 

Fig. 9 ToF-SIMS spectra of plasma-acetylene-coated silica (a) positive and (b) negative...

For silica in SBR, a polyacetylene coating gives the lowest filler-filler interaction, a good filler-polymer interaction, and the best dispersion compared to untreated and the other plasma-treated samples. However, for the stress-strain properties, the polythiophene-treated sample gives the best results. This shows the importance of sulfur moieties on the surface of the filler, which form a secondary network in the cured materials. In the blend of S-SBR and EPDM rubbers, the situation is less conclusive. The Payne effect, the bound rubber, and... 

The packing material first described for direct injection of biological samples was prepared by simply saturating the accessible adsorption sites of a Cis reversed-phase silica with human plasma proteins (105). After saturation, the human plasma proteins were denatured at the external surface, and their native conformation was destroyed. With this treatment, the proteins formed a hydrophilic layer with weak ion-exchange properties, which provided protection from contact with the sample proteins, whereas the alkyl ligands inside the pores remained unchanged and thus served for analyte retention. The retention behavior of the saturated phase did not alter with this treatment, but the efficiency was reduced dramatically. Such protein-coated columns have shown a lifetime of several months (106). 

A stereoselective GC method for determination of etodolac enantiomers in human plasma and urine was first reported as a preliminary method [35], and then as a validated method [36]. Sample preparation involved addition of (S)-(+)-naproxen (internal standard) and sodium hydroxide to diluted plasma or urine. The samples were washed with diethyl ether, acidified with hydrochloric acid, and extracted with toluene. ( )-(+)-naproxen was used as a derivatizing agent to form diastereomeric derivatives of etodolac. The gas chromatograph system used in this work was equipped with fused-silica capillary column (12 m x 0.2 mm i.d.) coated with high-performance cross-linked methylsilicone film (thickness 0.33 pm) and a nitrogen-phosphorous detector. The operating conditions were injector 250°C detector 300°C column 100-260°C (32 °C/min). 

Gas-phase nucleation Flame synthesis of particles (e.g., carbon black, silica) cluster formation in chemical vapor deposition manufacture of high-purity silicon cluster structure and energetics plasma synthesis of refractory materials and coatings. 

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