Carbon black reinforcing rubber material

Above a critical hller concentration, the percolation threshold, the properties of the reinforced rubber material change drastically, because a hller-hUer network is estabhshed. This results, for example, in an overproportional increase of electrical conductivity of a carbon black-hUed compound. The continuous disruption and restorahon of this hller network upon deformation is well visible in the so-called Payne effect [20,21], as represented in Figure 29.5. It illustrates the strain-dependence of the modulus and the strain-independent contributions to the complex shear or tensUe moduli for carbon black-hlled compounds and sUica-hUed compounds. 

The first process of this type utilized gases as raw materials and produced carbon blacks for rubber with only moderate reinforcement properties at a maximum yield of 30%. The changeover to liquid and melting raw materials increased the yield of carbon black for rubber to 40 to 70% and enabled a much broader range of raw of products to be produced, so that this type of raw material is now almost exclusively used e.g. aromatic compound-rich viscous residues from oil refineries, coking plants, catalytic crackers and steam crackers for the production of ethene and from the catalytic synthesis of petrol. 

Even this definition needs to be classified [7, 8]. To some researchers it is still too broad because it includes many materials that are not usually thought of as composites such as concrete, copolymers and blends, reinforced plastics, and carbon-black-filled rubber. On the other hand, some of the more recent composites are excluded from the category of composites if this definition is strictly applied. For example, many particulate-type composites such as dispersion-hardened alloys and cermets have composite structures that are microscopic rather than macroscopic [2,8]. In some cases, the composite structures are nano-scopic, with the physical constraint of several nanometers as the minimum size of the components [9-16]. The terms... 

Rubber threads are susceptible to oxidative degradation, and high concentrations of antioxidants are added to the mixture to make the high surface area fibers more resistant. Pigments, such as titanium dioxide, are used as fillers or to impart whiteness to the thread. Carbon black reinforcement is used in colored rubber materials. Other agents include accelerators and activators to promote the vulcanization process. With all the additives, a typical high grade rubber thread contains less than 85% elastomer. 

The important characteristics of acrylate rubbers are good oil resistance and good heat resistance carbon black reinforced materials age very well in air up to about 200 C. It is these properties which account for the major use of acrylate rubbers, i.e., in oil seals for automobiles. Polyacrylates are fairly readily hydrolyzed to poly(sodium acrylate) by heating with aqueous sodium hydroxide for a few hours. 

Crude petroleum is obviously vital to the rubber industry. All of the synthetic raw elastomers and the vast majority of the rubber compounding ingredients are directly dependent on petroleum as a feedstock. It is by far the most critical natural raw material for successful rubber production and fabrication. Without crude oil, at least in the short term, there would be no rubber industry as we know it today. There would be only natural rubber for the rubber base, no rubber accelerators, no effective antioxidants, no furnace carbon black reinforcement, and so on. In the long term, however, it would be possible to manufacture organic monomers and organic rubber chemicals from other carbon sources such as agricultural products and coal tar. However, this would result in major economic dislocations and require the development of a new infrastructure. 

Reinforcing Agents. To increase the cohesive strength of an unsaturated rubber adhesive, carbon black is the material of choice. It must be added to the rubber in an internal mixer or on a two roll mill before the rubber is dissolved in the solvent. Such additions do, of course, stiffen the dried adhesive, and some softener may be required to balance this, though this could adversely affect adhesive performance. Carbon black used to be added by means of whole tire reclaim but, as noted in the introduction, the practice is declining. 

The mechanical properties and cross-linked network structure of a peroxide-cured nitrile rubber containing magnesium methacrylate are investigated and discussed. Some typical properties of the material are compared with those of carbon black reinforced nitrile rubber. 8 refs. CHINA... 

Like NR, SBR is an unsaturated hydrocarbon polymer. Hence unvulcanised compounds will dissolve in most hydrocarbon solvents and other liquids of similar solubility parameter, whilst vulcanised stocks will swell extensively. Both materials will also undergo many olefinic-type reactions such as oxidation, ozone attack, halogenation, hydrohalogenation and so on, although the activity and detailed reactions differ because of the presence of the adjacent methyl group to the double bond in the natural rubber molecule. Both rubbers may be reinforced by carbon black and neither can be classed as heat-resisting rubbers. 

The pneumatic tire has the geometry of a thin-wallcd toroidal shell. It consists of as many as fifty different materials, including natural rubber and a variety ot synthetic elastomers, plus carbon black of various types, tire cord, bead wire, and many chemical compounding ingredients, such as sulfur and zinc oxide. These constituent materials are combined in different proportions to form the key components of the composite tire structure. The compliant tread of a passenger car tire, for example, provides road grip the sidewall protects the internal cords from curb abrasion in turn, the cords, prestressed by inflation pressure, reinforce the rubber matrix and carry the majority of applied loads finally, the two circumferential bundles of bead wire anchor the pressnrized torus securely to the rim of the wheel. 

A typical tire rubber formulation for tire tread will contain various rubbers, mainly styrene-butadiene (50%) and cA-polybutadiene (12%), various processing aids (2%), softeners (3%), vulcanizing agent (mainly sulfur 1%), accelerators, and reinforcing filler (namely carbon black 30%) so that by bulk, carbon black is the second most used material. 

HAF (high-abrasion furnace black) highly reinforcing furnace carbon black increasing resistance of a rubber compound to abrasion, heat aging exposure of polymeric materials under specified conditions (temperature, time, presence or absence of air or oxygen, etc.) then testing them... 

---