Fillers for elastomers

Carbon blacks are the most widely used fillers for elastomers, especially vulcanised natural rubber. They cause an improvement in stiffness, they increase the tensile strength, and they can also enhance the wear resistance. Other particulate fillers of an inorganic nature, such as metal oxides, carbonates, and silicates, generally do not prove to be nearly so effective as carbon black. This filler, which comes in various grades, is prepared by heat treatment of some sort of organic material, and comes in very small particle sizes, i.e. from 15 to 100 nm. These particles retain some chemical reactivity, and function in part by chemical reaction with the rubber molecules. They thus contribute to the crosslinking of the final material. 

The metathesis products, the polyalkenamers, exhibit excellent properties as polymeric fillers for elastomers. The interests of the rubber industry stimulate research orientation to this kind of ring-opening polymerization (see, for example, refs. 344-346). 

Langford Clay. [R.T. Vanderbilt] Soft kaolin inert filler for elastomers, nonblack stocks. 

Very finely divided colloidal silica powders can also be obtained by treating certain silicate minerals such as clay or calcium silicate with acid, followed by suitable heat treatment in an alkaline medium. Similarly, finely divided colloidal silicas can be produced by precipitating silica from a solution of sodium silicate with carbon dioxide. Such precipitated silicas are commonly used as reinforcing fillers, for elastomers because they are extremely finely divided, and the ultimate particles are easily broken apart. Finely divided aerogels of silicas may be employed, such as those described by Kistler in U.S. Pat. Nos. 2,093,454 and 2,249,767. 

Uses Rheok) control agent, reinfordng agent, filler for elastomers, dental compels. flow aid for toners, powd. coatings anfisettling agent in coatings adsorptive carrier base for perfumes, pestiddes, veterinary prods., etc. also in defoamers, liq. resins, silicones, thermal insulation Preppies Wh. flufly powd., odorless 0.2-0.3 avg. particle size insol. in water sp.gr. 2.2 bulk dens. 3 Ib/ff surf, area 215 030 m /g pH 4.8-... 

Carbon black is the most important filler for elastomers and in particular NR. It can bind strongly with hydrocarbons. Carbon black gives protection from ultraviolet radiation that would otherwise cause chemical degradation. Carbon black in common with other fillers will reduce gas permeation that is critical for... 

Fillers. Fillers for elastomers are not generally used just to fill space and cheapen the compositions. They are very important to modify the properties of rubber compositions in very positive ways. This is especially true for the so-called reinforcing fillers. Their presence in the compound can improve the strength- and durabihty-related properties of vulcanizates and can strongly enhance processing characteristics. The choice and amount of filler can have a profound effect on vulcanizate properties. These effects depend on several factors level of use (concentration), primary particle size, surface area (inverse function of primary particle size), and structure (shape factor, e.g., spherical, chain or rod-like, plate-like, and so forth). 

A short study was made as to the ability of these reactive particles to act as reinforcing fillers for elastomers. A styrenic filler with peracetate functionality was substituted for a high abrasion furnace black in a typical SBR formulation. Only 28 phr of the styrenic filler was used as compared to 40 phr of the carbon black to compensate for the density differences. As can be seen by the results of Table 9, the reactive styrenic particle acts as a reinforcing filler for SBR. 

Stabilization of silica-thickened grease with basic aluminum stearate probably - involves adsorption of the aluminum on the silica with the fatty add anions attached (503). Silica fillers for elastomers are improved by rendering the surface organophilic with basic chromium complexes of the type... 

ZnO has a hardness of 4.5 it is used mainly as a filler for elastomers, PP, and polyesters. The composite made of PP filled with ZnO shows a great resistance to moisture and weathering. ZnO can also react with free carbonyl groups in polyester resins, leading to composites with remarkable physical properties. 

---