Natural rubber also bound

Another attempt by Tricas et al. to modify the surface of carbon black was by the plasma polymerization of acrylic acid [34]. Treatment with acrylic acid made carbon black hydrophilic. Plasma-coated carbon black was mixed with natural rubber and showed increased filler-filler interaction. The bound rubber content was reduced after the surface treatment of the filler. The authors also concluded that the surface of the carbon black was completely covered by the plasma polymer film, preventing the carbon black surface from playing any role in the polymer matrix. 

Solvents produce different effects than do corrosive chemicals. Both silica and carbon black filled natural rubbers were more resistant to solvents than unfilled rubber. Also, the cure time was important, indicating that the bound rubber plays a role in the reduction of a solvent sorption. The diffusion coefficient of solvents into rubbers decreases with longer cure times and higher fillers loadings. Polychloroprene rubber swollen with solvent has a lower compression set when it is filled with carbon black. 

Diamine salts of fatty acids are used as multifunctional additives in natural rubber compounds filled with carbon black.They affect the elastomer-carbon black interface. With an increased concentration of multifunctional additive, the concentration of bound rubber decreases but dispersion of carbon black is improved. In silica filled rubber, multifunctional additive also improves the dispersion of silica, but in addition, it decreases the negative influence of silica filler on vulcanization rate. 

Hindered phenols, like 2,6-di-rert-butyl-p-cresol, which in an oxidizing environment and at high concentrations transforms to stilbenequinone. This species absorbs visible light, and therefore adds to discoloration. It has also been found that hindered phenols, containing ortho or para methyl groups react with natural rubber latex in the presraice of free radicals. This bound antioxidant is much more efficient than conventional antioxidant [123]. 

Concerning the growth and the nature of the bound rubber, much insight may be gained from the book by Donnet and Voet [29]. The bound rubber also forms from rubber... 

In order to establish the nature of the bonds, the specimen is also treated with ammonia. Under these conditions only chemically bound rubber remains absorbed on the fillefs surface and physically bound polymer is extracted. Silica-rubber gels contain mostly physical bonding. 

Alkyl Bound to Miscellaneous Elements. Several compounds in which alkyl is bound to a sulfur atom have become quite important in recent years for example, the mercaptans, such as amyl and ethyl mercaptan, are used as warning agents in natural gas because of their intense and disagreeable odor. Mercaptans are also employed in organic syntheses as, for instance, the manufacture of sulfonal by the condensation of ethyl mercaptan (ethanethiol) with acetone, followed by oxidation. In recent years a very considerable amount of mercaptan has been used for controlling the polymerization reaction between butadiene and styrene to form synthetic rubber (GR-S). 

Bound rubber determination is also applied to silica compounds, even if the numerous possible interactions naturally limit the interpretation of the values [127,128]. 

The chemical and physical nature of the carbon-black surface is known to influence reinforcement strongly. There is no doubt that polymer interacts very strongly with the surface of carbon black to form a layer of bound rubber that cannot easily be removed. The attraction forces are considered to be primarily physical in character but many reactive chemical sites [33] are also present on the surface. These may play an important role on vulcanisation behaviour. The surface of carbon blacks are also known to contain varying degrees of porosity (from surface area measurements) [48]. 

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