Carbon-Black-Filled Natural Rubber

Examples of Cure Systems in NR, SBR, and Nitrile Rubber. Table 6 offers examples of recipes for conventional, semi-EV, and EV cure systems ia a simple, carbon black-filled natural mbber compound cured to optimum (t90) cure. The distribution of cross-links obtained is found ia Figure 9 (24). 

Table 3. Properties of Carbon Black-Filled Natural Rubber Vulcanizates With Various Cure Systems ...

FIGURE 1.13 Knotty tearing at the tip of an edge cut, 2.8 mm long, in a sheet of a carbon-black-filled natural rubber vulcanizate, broken in tension. (Reproduced from Hamed, G.R. and Park, B.H., Rubber Chem. TechnoL, 72, 946 (Figure 6), 1999. With permission.)... 

Fig. 31. Stacked plot of the heteronuclear two-dimensional J-resolved spectrum of cured, carbon black filled, natural rubber. The proton flip experiment was used with high-power proton decoupling during the detection time. The experiment was performed with the sample spinning at the magic angle (reprinted from Ref. 1911 with permission)...

Several NMR relaxation studies using carbon-black-filled natural rubber (NR), EPDM and butadiene (BR) rubbers have shown that a layer of immobilised, tightly bound rubber is formed on the carbon black surface [20, 62, 79, 87, 89] (Figure 10.9). 

Carbon Black Filled Vulcanised Natural Rubbers... 

Fig. 12a,b. Fitting functions of storage and loss moduli of carbon black filled natural rubber according the L-N-B-model (from [90])... 

Antioxidant for natural and synthetic rubber, tires, automotive and appliance molded goods, polyamides and carbon black filled olefin formulations for use in geomembranes, wire and cable jacketing, and irrigation piping. 

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. 

Applications . NMR has found the following applications in filled systems carbon black adsorption of SBR, the effect of carbon black loading on cure rate of natural rubber, gel-like behavior of polybutadiene/carbon black mixtures, structure and dynamics of carbon black filled rubber vulcanizalcs, " interaction of... 

In the present paper, which is intended as a review of more recent progress only, emphasis is placed on the physical approach, but not to complete exclusion of the nature of the polymer-filler bond. Because of the overwhelming importance of carbon black as a reinforcing filler, and because most of the pertinent literature on reinforcement concerns carbon black filled rubbers, much of the discussion will be directed to carbon black reinforcement. However, the principles involved are general and apply qualitatively also to other fillers. 

Volnme resistivities have been reported on phenol-formaldehyde [37], carbon fibre reinforced ABS terpolymer [35], natural rubber [38], polystyrene (PS) [35], HDPE-natnral fibre composites [34], carbon black filled PP-epoxy-glass fibre composites [5], XLPE [32], nanoclay reinforced EPDM-g-TMEVS [31] and epoxy resin/PANI blends [33]. 

The effect of cure temperature on the cure kinetics and cure state profile of a simple carbon black filled, sulfenamide/sulfur cured natural rubber compound is shown in Figure 6 (16). As shown in the growth of the cure state, an article which would require 110 min to cure to its maximum cure state at 125°C can be cured at 135°C in 50 min, at 150°C in 18 min, at 165°C in about 7 min, and at 182°C in about 3 min. However, the maximum state of cure achieved keeps dropping as cure temperature increases. 

Table 19 illustrates formulas for conventional, semi-EV, and EV cure systems in a simple, carbon black-filled natural rubber compoimd cured to optimum cure (t90). 

Perhaps the largest volume commercial production of particle-filled polymers is carbon- or graphite-filled rubbers. Carbon blacks are widely used in natural and synthetic rubbers and convey significant improvements in modulus, abrasion resistance, and tear strength as well as additional thermal and electrical conductivity. Carbon blacks are uniquely efficient in these respects the reasons for this are still the subject of debate. A very recent review by Rigbi is an excellent compilation of current theory and experiment. An earlier review by Medalia ... 

Fig. 5 Dispersion rating of N-330 carbon-black-filled natural rubber as a function of mixing time.

In this work [91], the effects of the quality of carbon black dispersion on the dynamic shear moduli of uncured, carbon-black-filled, natural rubber compositions were investigated. Effects due to changes in temperature,... 

Laraba-Abbes F, lenny P, Piques R (2003) A new Tailor-made methodology for the mechanical behaviour analysis of rubber-like materials n. Application to the hyperelastic behaviour characterization of a carbon-black filled natural rubber vulcanizate. Polymer 44 821-840... 

Harwood JAC, Payne AR (1966) Stress softening in natural rubber vulcanizates III. Carbon black filled vulcanizates. J Appl Polym Sci 10 315-23... 

It appears that the special property of the carbon-black filled rubber merely enhances the effect by further increasing the constriction resistance. The imperfect nature of the physical contact between bodies transmitting a normal load Is probably the main cause of this phenomenon. The high contact resistance enables a fairly large share of the applied voltage to act across the contact surfaces. The real areas of contact should be able to withstand a sufficiently large voltage. In this context, the effect described here Is somewhat similar to the Johnsen-Rahbek effect described by Hoim. ... 

---