Silane treated clay

Treatment of water-washed hard china clays with silanes with pendant amino or mercapto groups enables them to give improved reinforcement to rubber compounds. Silane-treated clays give compounds with lower viscosity, considerably higher modulus and tensile strength and lower compression set than compounds containing untreated clays. 

The effect of high shear mechanical mixing and soni-cation methods on the physical properties of the nanocomposites has been analyzed [84] using modified clays with a quaternary ammonium salt and calcium carbonate [85] and silane-treated clays [31]. Although the nanoclay is usually chemically modified to make it organophilic and compatible with the polymer matrix, untreated MMT was... 

D.A. Skelhorn, Proceedings of Developments In The Use Of Silane Treated Clay In Cable Insulations, International Rubber Conference, Prague, Czechoslovakia, 1989. 

Over the past 25 years, a considerable amount of effort has been expended to develop and study high efficiency, reinforcing mineral fillers as partial replacement for the carbon blacks. Even though it has been but moderately successful the impetus to continue this work for economic considerations is obvious. In his paper on silane treated clays as reinforcing fillers for rubber. Dr. Plued-demann will discuss the nature and extent of adhesion between matrix and filler. This is a subject which has been and still is highly controversial. 

Clay hllers were surface modihed with TMPTA or triethoxyvinyl silane (TEVS) followed by EB irradiation by Ray and Bhowmick [394]. Both the untreated and treated fillers were incorporated in an ethylene-octene copolymer. Mechanical, dynamic mechanical, and rheological properties of the EB-cured unfilled and filled composites were studied and a significant improvement in tensile strength, elongation at break, modulus, and tear strength was observed in the case of surface-treated clay-filled vulcanizates. Dynamic mechanical studies conducted on these systems support the above findings. 

Clay minerals are widely used in the filler industry and the production of the various types has been described by Hancock and Rothon [85]. The products available range from unaltered kaolin to products produced by calcination. Kaolin deposits are widespread throughout the world. While simple clay minerals are extensively used as fillers in elastomers, their use in thermoplastics is more restricted and the principal products used are those obtained by calcination of ka-olinite. Thus metakaolinite finds application in PVC and silane treated calcined clay in polyamides. The production of these forms only is discussed below. 

Special surface modifications are available to further improve reinforcement. The objective of the surface treatment is to increase filler loading and/or improve physical properties without loss of rheological characteristics. A variety of surface-modified kaolins have been introduced including clays treated with silane, titanate, polyester, and metal hydroxide. Silane-treated kaolin is used in applications requiring maximum aging characteristics in the service environment. 

When silane-treated, calcined clay can be used in polyamide and polybutylterephthalate (PBT) moulding compounds and in very high-voltage rubber cable insulation. Each application needs a silane with a different functionality. 

Surface-treated clay - This is processed kaolin diat has been surface modified (e.g., with stearates or silanes) to improve compatibility with and performance in organic matrices. 

The high modulus with low hysteresis of the treated clays vs. carbon black, as seen in a natural rubber compoimd in Table 7, suggest that the silane mediated polymer-clay bond is stronger than the polymer-black bonds at the carbon black active sites. Deformation results in loss of fewer polymer-filler bonds with the treated elays, so that energy loss as heat is less compared to the carbon black. This stronger polymer-clay bond is also consistent with the higher modulus and abrasion resistance. 

The calcined clays such as Whitetex are neutral and have lower water absorption and better electrical properties, but slightly lower physical properties. Vinyl silane surface treated calcined clays such as Translink 37, amino-silane treated calcined Translink 445 have even better water resistance and electrical properties. 

Silane treated, calcined clay 70.0 Mineral filler Level 1 filler evaluation... 

Non-black fillers may also be employed, but it is important to use neutral or medium high pH grades such as silane-treated calcined clay, synthetic sodium aluminum silicate, platy talc, neutral pH silicas, diatomaceous earth, hydrated aluminum silicate, calcium meta silicate, precipitated calcium carbonate, and so on. An indication of non-black filler requirements for one point of hardness increase is shown in Table 5.10. 

With filled compounds, it is necessary to avoid consumption of the adhesion promoter through coupling instead to the filler surface. Thus, calcimn carbonate is the preferred filler with silane adhesion promoters. Calcined clay or ATH may be used if previously silane-treated. Compounds containing reactive silanes should be processed promptly. The use of titanates or zirconates as adhesion promoters should be carried out in close cooperation with the additive supplier. 

Organofunctional silanes are used to promote polymer-to-filler bonding with clay or siHca fillers. Vinyl silanes are used in peroxide-cured wire insulation to promote stronger bonding with calcined clay fillers. Mercapto silanes are used to treat kaolin clay in sulfur-cured compounds. 

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