Reinforcing silica for rubber

The first reinforcing silica for rubber, which was in the form of a calcium silicate and known as Silene, was introduced to the U.S. market as early as 1939 (II). The first reinforcing fillers for rubber articles available in West Germany after the Second World War were also calcium and aluminum silicates. The production of Hi-Sil, a silicate with a high silica content, started in 1946 (12). The first pure precipitated silica was brought onto the European market in 1953 and was called Ultrasil VN 3 (13). 

Antimony oxide, brominated compounds, reinforcing silicas for rubbers, continuous strand mat... 

Very finely divided amorphous silica containing a small amount of carbon can be produced by controlled incineration of rice hulls. It is reported to be a reinforcing filler for rubber competitive with thermal carbon blacks (494). 

In the early 1990s, a new generation of precipitated silicas was developed the so-called highly dispersable silicas (HDS) (61-65). This class provides another vital attribute of a reinforcing filler for rubber easy dispersabihty at high loadings to submicron sizes. 

The rubber chemist has recognized and reacted to the growing trend to employ silica as reinforcing filler for rubber with development of multiple silane ester coupling agents and alkyl silane process aids for improved processability and performance. 

Synthetic silicas and silicates are powerful reinforcing agents for rubber. These materials may be classified according to their method of production, thermally produced (pyrogenic or fumed) silicas and wet-produced (precipitated) silicas [51]. 

Generally speaking, commercial rubber products are manufactured as a composite from a rubber and a nano-filler, which is in a group of fillers of nanometer size (mainly, carbon black and particulate silica). For an example, a pneumatic tire for heavy-duty usages such as aircrafts and heavyweight tracks is made from natural rubber (NR) and carbon black and/or silica. Their reinforcing ability onto rubbers makes them an indispensable component in the rubber products [1,2]. 

Fumed silica is prepared by burning volatile silicon compounds such as silicon tetrachloride. This type of silica contains less than 2% combined water and generally no free water. It reacts readily with hydroxyl groups. The particle size is in the region 5-10 nm. Fumed silicas are not generally used in conventional rubber compounding but find application with silicone rubber. The recognised surface area values for best reinforcement of silicone rubber by an amorphous silica lies between 150-400 m2/g. 

Abstract Plasma polymerization is a technique for modifying the surface characteristics of fillers and curatives for rubber from essentially polar to nonpolar. Acetylene, thiophene, and pyrrole are employed to modify silica and carbon black reinforcing fillers. Silica is easy to modify because its surface contains siloxane and silanol species. On carbon black, only a limited amount of plasma deposition takes place, due to its nonreactive nature. Oxidized gas blacks, with larger oxygen functionality, and particularly carbon black left over from fullerene production, show substantial plasma deposition. Also, carbon/silica dual-phase fillers react well because the silica content is reactive. Elemental sulfur, the well-known vulcanization agent for rubbers, can also be modified reasonably well. 

The Payne effect of carbon black reinforced rubbers has also been investigated intensively by a number of different researchers [36-39]. In most cases, standard diene rubbers widely used in the tire industry, bke SBR, NR, and BR, have been appbed, but also carbon black filled bromobutyl rubbers [40-42] or functional rubbers containing tin end-modified polymers [43] were used. The Payne effect was described in the framework of various experimental procedures, including pre-conditioning-, recovery- and dynamic stress-softening studies [44]. The typically almost reversible, non-linear response found for carbon black composites has also been observed for silica filled rubbers [44-46]. 

Akrochem RubberSil. [Akrochem] Precipitated amcxphous silica reinforcement for rubber mech. goods, tires, footwear. 

Hubersil . [J.M. Huber] Hydrated silica reinforcing filler, carrier for rubber parts incl. hose, belting, molded and extruded parts, tires, footwear, wire and cable, thermqilastic elastomers, caulks and sealants. 

Some of the applications Include contact lenses, medical tubing and protective gas masks. The silicone rubber for these applications is optically clear because the silicone polymer and the reinforcing silica used to prepare the rubber are isorefractive at a specified temperature, usually about 25 C. The polymers which have been used are copolymers with sufficient phenyl substitution to raise the refractive index, from 1.4023 (for PDMS) to approximately 1.43 which is the refractive index of tri methyl si lyl treated fumed silica (e.g., Cabosll S-17). Such copolymers are prepared by copolymerizing (Me2S10)x and (PhMeSiO) or (Ph2S10)x using equilibrium conditions. 

Chem. Descrip. Untreated fumed silica, undensed CAS 112945-52-5 EINECS/ELINCS 231-54S4 Uses Reinforcing agent for adhesives, coatings, defoamers, elastomers, lubricants, plastisols, liq. resins, sealants, silicones, cosmetics, pharmaceuticals food pkg. adhesives, coatings, paper/paperboard, cellophane, film, rubber articles detoamer in fo< -contact coatings, paper/paperboard... 

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