Silica compound

Vitreous silica produced by this route contains small amounts of impurities such as Fe, Cr, A1 and Ca. To achieve metal ion impurities < 10 % the synthetic hydrolysed silane process is used. Organic silica compounds or SiCl4 are hydrolysed in a flame to produce fine molten droplets of SiOj which is deposited on a cold base. 

The same is observed if the maximum speed of the speed distribution function is varied and the acceleration is kept constant. The tire life is drastically reduced and the rating of the silica compound reverses in relation to the OESBR as the speed is increased. 

Rubber Mixing with Emphasis on Silica Compounds.804... 

The temperature window for mixing of silica compounds is rather narrow, limited by the decreasing silanization rate and increasing risk of scorch. High temperatures improve the sUaniza-tion rate due to the temperature dependence of the reaction and the enhanced rate of alcohol... 

Silica compounds are generally processed in conventional internal mixers, preferably with intermeshing rotors. These mixers are designed and optimized for carbon black-fiUed compounds in which mixing is based only on physical processes. When a silica-silane reinforcing system is used, additionally a chemical reaction, the sUanization, occurs. One of the main influencing factors of the silanization reaction is the concentration of ethanol in the compound as well as in the mixer [25,26]. As the silanization finally reaches an equilibrium, low concentrations of ethanol in the compound are expected to enhance the reaction rate. 

Another measure to improve the removal of ethanol is air injection into the mixer during the silanization step. Air can be injected from the bottom part of the mixer using existing valves without any special outlet for the injected air. In these experiments air injection is switched on once the compound reached the silanization temperature (145°C) and the rotor speed is adjusted in order to maintain the silanization temperature. Figure 29.13 shows the properties of this compound compared to a compound that was silanized under the same conditions except with air injection switched off. Air injection lowers the Payne effect, Mooney viscosity, and water content in the compound, and ethanol removal is more effective. All other properties are comparable to the properties of a standard silica compound. 

In the presence of ZnO, the dump temperature is a parameter of paramount importance in mixing of a silica compound containing a couphng agent with a polysulfidic moiety The sulfur eliminated from the coupling agent causes premature scorch in the presence of ZnO. This problem is partially solved when ZnO is added in the productive mixing step on the two-roU mill. 

The efficiency of the silanization reaction is increased by aU measures enhancing devolatilization of ethanol from the silica compound in the mixer. One possible measure is the reduction of the ethanol concentration in the void space of the mixer, thus increasing the driving force for mass... 

Dierkes, W., Economic mixing of silica compounds. Print Partners Ipskamp, Enschede, The Netherlands, 2005. 

This chapter deals with recent developments of rubber mixing and calendering. Rubber extm-sion is discussed elsewhere in this book. Although it dominates mbber mixing in the last ten years, the mixing of silica-filled tread compounds is only slightly discussed in this chapter, since another chapter in this book totally covers the mixing of silica compounds. 

Triple-Tread, Asymmetrical Tread, Chimney Design, Silica Compounds.1013... 

Revolutionary tire designs for high-tech passenger car radial (PCR) tires drives the developmental pace of the tire equipment manufactures. Triple-tread, asymetrical tread, or highly loaded silica compounds have a consequential impact on the extrasion machinery. In this context the design of the extmsion head and the extmders itself requires adaption to the new, challenging tire technology of today. 

Today, highly loaded silica compounds with relatively low carbon black content for tread profiles are becoming the standard for high-tech PCR tires. 

The PVD process by means of electric arc evaporation has attained a high degree of importance in deposition of hard layers on an industrial scale. The hardness achieved is a minimum of 2100 HV. Compare this to the standard nitriting process which provides a hardness of about 900 HV or the stelliting process which offers about 500-600 HV. Extmsion screws treaded with this special process in the tire industry have seen a much improved wear life when processing highly filled silica compounds or very hard apex compounds. 

PVD-coated screws for highly loaded silica compounds are mainly used in Berstorff Multiplex extmsion lines. With these lines, the different compounds are led together and shaped in special prohle extmsion dies. Flow channels with optimized geometry ensure a uniform material flow of the individual prohle components. The extmsion tools Berstorff developed for this purpose are... 

TS-1 has been obtained by the hydrothermal crystallization of a gel obtained from TEOS and TEOT in the presence of tetrapropylammonium hydroxyde (TPA-OH). The structure of TS-1 has been demonstrated by X-ray diffraction (XRD), energy dispersive X-ray (EDX), microprobe analysis, and 29Si magic-angle spinning (MAS) NMR spectroscopy. Furthermore, an absorption band in the IR spectrum at 960 cm-, present in TS-1 and absent from that of silicalite, was initially considered a fingerprint for the characterization of TS-1. However, later work (discussed below) has shown that this band is also present in many other silica compounds, and therefore its relation to framework Tilv is not straightforward. 

Once the contents of the container are evenly distributed, the adhesive or sealant material can be removed. The use of pumps for transferring the adhesive or sealant has several drawbacks. Filled compounds have an abrasive action on the moving parts. This is particularly true with fillers such as silica. Compounds that polymerize easily will tend to begin their polymerization due to friction within the pump. This will gum up the moving parts and make them inoperable. Therefore, transfer is best done under some type of pressure. 

A new class of hydride organic/silica compounds such as organically bridged polysilsesquioxanes 213 were prepared from the hydrolysis and condensation of triethoxysilanes 212 linked by a hydrocarbon spacer, as shown in Equation (41). 

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