Silica coupling agents

Uses Monomerfor silicone prods. surface treatment agent (silica) coupling agent blocking agent release agent lubricant herbicide... 

The ease of mixing of CSDP was demonstrated by a lower mixing torque and a shorter incorporation time, compared to the counterpart grade of carbon black or silica-coupling agent. The resulting CSDP compound showed better dispersion. 

The order of addition was rubber, carbon black, silica, coupling agent and a mixture of zinc oxide and stearic acid. The filler and other additives were charged very quickly in succession. 

The composition of an epoxide moulding material will greatly depend on the specific application, and this has been discussed at length. ". The resin may be of the epoxide novolac type and there will also be present hardeners, fillers (such as silica), a silane coupling agent, pigment, flame retardant and a wax release agent. 

Fig. 18. Yield strengths in three-point bend tests of highly filled composites of polyfvinyl butyral) and silica particles treated with methylsilane and octylsilane coupling agents to varying degrees of surface coverage vs. work of adhesion measured independently using IGC. Redrawn from ref. [90].

Various additives and fillers may be employed. Calcium carbonate, talc, carbon black, titanium dioxide, and wollastonite are commonly used as fillers. Plasticizers are often utilized also. Plasticizers may reduce viscosity and may help adhesion to certain substrates. Thixotropes such as fumed silica, structured clays, precipitated silica, PVC powder, etc. can be added. Adhesion promoters, such as silane coupling agents, may also be used in the formulation [69]. 

The formation of these polar groups contributes increased adhesion. Observation of disappearing vinyl groups in the silane coupling agent and of the formation of polystyrene in the silica by FTIR analysis (Fig. 15) have confirmed the occurrence of a reaction between the polymer and the silane coupling agent [77]. 

These poly(2-alkyl-2-oxazoline) silane coupling agents were copolycondensed with tetraethoxysilane by acid-catalyst to produce poly(2-alkyl-2-oxazoline)-modified silica gel. The composite gel from 2-ethyl-2-oxazoline was also homogeneous and transparent glass. Poly(2-alkyl-2-oxazoline)-modified silica gels, especially gels based on poly(2-ethyl-2-oxazoline) absorbed water and also organic solvents such as DMF or alcohols as shown in Table 7. This result means that the obtained composite gel shows the amphiphilic adsorption property. 

SBR Cariflex S1215 BR Buna CB 10 Silica, Perkacil KS 408 Zinc oxide Stearic acid Aromatic oil Coupling agent, TESPT Santoflex 6PPD Wax PEG 4000 Perkacit TBBS Perkacit DPG Sulfur... 

Silica is unique among nonblack fillers. Its reinforcing ability is comparable to that of carbon black, especially when mixed with a suitable coupling agent, and its transparency affords many products. Additionally, it is chemically synthesized, which means that a wide range of silica (in terms of diameter, surface area, or surface activity) may be produced depending on the reaction routes and reaction conditions. 

Prior to the chemical reaction of the silane with the silanol-groups on the sUica surface, the silane molecule has to make contact with the sUica surface by adsorption. Then the chemical reaction of silica with an alkoxy-silyl moiety of the coupling agent takes place in a two-step, endothermic reaction. The primary step is the reaction of alkoxy-groups with silanol-groups on the silica filler surface [4]. Two possible mechanisms are reported ... 

The polysulfidic moieties of the silanes are unstable, and cleavage of the sulfur groups results in active sulfur species. A notorious problem with this kind of coupling agents is the balance between its reactivity towards the silica, requiring a temperature of at least 130°C to obtain an acceptable speed, and its eagerness to react with the rubber polymer, which starts to become noticeable at temperamres above 145°C. Furthermore, the primary and secondary reactions are chemical... 

The incorporation of reinforcing hllers into rubber results in most cases in an increase of the storage and loss moduli, G and G", and an increase in hysteresis, as quantihed by the loss angle 8, where tan 8 is C jG. When properly dispersed and coupled to the mbber matrix via a coupling agent, as represented by a low Payne effect, silica also shows less hysteretic loss at elevated temperatures. 

ZnO influences the characteristics of a compound twofold Primarily, ZnO influences the kinetics of the silica-silane reaction. Secondly, ZnO enhances the scorching behavior of a sulfur-containing coupling agent. This effect is clearly visible when looking at the G at 100% strain and the 300% modulus. 

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. 

Increasing price of crude oil has built up pressure on tire and automobile industry to develop low rolling-resistant tire with better traction. Combination of carbon and silica with coupling agent (dual filler technology) shows low RR with better traction and skid resistance in tire tread compound. Carbon black developed by plasma process and nanostructure black are other new significant developments in filler technology. 

Carbon black-silica dual phase fillers reduce hysteresis while maintaining or improving abrasion. This system is less expensive as coupling agent requirement is less and produces semicon-ductive product compared to full silica-filler system. Dual phase filler is less abrasive to the processing equipment compared to the usage of silica filler alone, but use of dual phase filler increases cost of compound compared to traditional carbon black. 

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