Tread grades

The consumption of the vanous carbon black grades can be divided into tread grades for tire reinforcement and nontread grades for nontread tire use and other mbber appHcations. Table 9 shows the distnbution of production of types for these uses. In the United States 55% production is for tread grades. In Western Europe tread-grade production is 64%, and in Japan it is 60%. 

Limiting our discussion to a carbon black manufacturing system for the production of tread grades in a furnace reactor, these systems have been discussed in detail in a number of articles, viz., Smith and Bean (35), Austin (4), Burgess (5), and Stokes (36), just to name a few. 

In summary, we will review carbon black classifications and their properties in rubber. The three most important properties are particle size, structure, and surface area. We will discuss only the tread grades. All of the tread grades of carbon black fall within the range of 20 nm. to 40 nm. 

Because of the wide variations in operating conditions, tread and carcass blacks cannot be made in the same reactor however, all tread grades can be produced in the same reactor as is the case with all carcass grades. Unfortunately, exact reactor construction details and operating details are proprietary information and cannot be revealed however, exact internal configuration, dimensions, oil spray pattern, and burner design are all extremely critical for optimum quality and yields. One reactor will produce from 20,000-40,000 lbs/day, and a unit consists of from 4 to 5 reactors, discharging into common downstream facilities. 

Tread-grade carbon blacks can be selected to meet defined performance parameters of rolling resistance, traction, wear, etc. 

Figure 9.5 illustrates the general trends for tread-grade carbon black loading and the effect on compound physical properties. As carbon black level increases, there are increases in compound heat buildup and hardness and, in tires, an increase in rolling resistance and wet skid properties. Tensile strength, compound processability, and abrasion resistance, however, go through an optimum after which these properties deteriorate. 

In some cases, it can also be possible to use TGA to obtain a measure of the relative proportions of two monomers in a copolymer. For example. Shield and Ghebremeskel [ 14] have obtained a quantitative determination of the amount of styrene in tyre tread grade, SBR rubbers. A methodology was established for determining the styrene content from the magnitude of the shifts in the polymer pyrolysis region of the TGA curve. 

A.C. Patel, J.T. Byers. The influence of tread grade carbon blacks at optimum loadings on rubber compound properties. Rubb. India, 34 (4), 9-13,1982. 

Fig. 3. Electron micrograph of reiaforciag-grade of N399 tread black (100, OOOx ).

Specific Surface Area. The specific surface area of industrial carbon blacks varies widely. While coarse thermal blacks have specific surface areas as small as 8 m2/g, the finest pigment grades can have specific surface areas as large as 1000 m2/g. The specific surface areas of carbon blacks used as reinforcing fillers in tire treads lie between 80 and 150 m2/g. In general, carbon blacks with specific surface areas >150 m2/g are porous with pore diameters of less than 1.0 nm. The area within the pores of high-surface-area carbon blacks can exceed the outer (geometrical) surface area of the particles. 

S-SBR grades have excellent balance between wet traction and rolling resistance therefore, they can be used for low fuel consumption tire treads in all-season tires and high-quality rubber goods. In applications of S-SBR, carbon black and silica will often be added to enhance the property. 

As compared to natural rubber, epoxidized grades of natural rubber show improved reinforcement with silica without any coupling agent. Radial tyre tread prepared using formulations based on natural rubber with epoxide... 

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