Filler reinforcement carbon black

V. Jha, Carbon Black Filler Reinforcement of Elastomers, PhB Thesis, Bpt. of Materials, Queen Mary, University of London, 2008, pp. 159-206. 

The polymer-carbon black filler reinforcement depends widely on the polymer type, carbon black type and structure. Another factor affecting this reinforcement is the filler-filler interaction which leads to the formatimi of three dimensional aggregation structures within the bulk of the rubber matrix. Figure 12 shows the aggregation and agglomeration of carbon black in the rubber. These aggregations takes various shapes which may be spherical or ellipsoidal with different major and minor... 

Carbon Black, Fillers, Reinforcing Agents, and Coupling Agents... 

Reinforcing fillers (active) Fumed Silica (Si02) precipitated calcium carbonate (CaCOi) carbon black Thixotropic reinforcing agents (non-slump), adjustment of mechanical properties (cohesion) provide toughness to the elastomer as opposed to brittle materials. 

Biopolymers have diverse roles to play in the advancement of green nanotechnology. Nanosized derivatives of polysaccharides like starch and cellulose can be synthesized in bulk and can be used for the development of bionanocomposites. They can be promising substitutes of environment pollutant carbon black for reinforcement of rubbers even at higher loadings (upto SOphr) via commercially viable process. The combined effect of size reduction and organic modification improves filler-matrix adhesion and in turn the performance of polysaccharides. The study opens up a new and green alternative for reinforcement of rubbers. 

Carbon black is reinforced in polymer and mbber engineering as filler since many decades. Automotive and tmck tires are the best examples of exploitation of carbon black in mbber components. Wu and Wang [28] studied that the interaction between carbon black and mbber macromolecules is better than that of nanoclay and mbber macromolecules, the bound mbber content of SBR-clay nanocompound with 30 phr is still of high interest. This could be ascribed to the huge surface area of clay dispersed at nanometer level and the largest aspect ratio of silicate layers, which result in the increased silicate layer networking [29-32]. 

Substitution of carbon black filler (or a significant part of it) with white reinforcing fillers (e.g. silica), as carbon black has also been found to act as a nitrosating agent. 

The proven compounding practice for the natural rubber layer is to load it with 30 phr of graphite, 30 phr of semi-reinforcing carbon black filler and 50 phr of inert filler, china clay. A low sulfur curing system is adopted for heat resistance with a suitable antioxidant to prevent flex-cracking. A typical chlorine resistant soft natural rubber compound formula is given in Table 3.2. 

Reinforcement is not specific to any one polymer, filler or vulcanization system. For example, a highly reinforcing carbon black will reinforce all rubbers to a similar (but not necessarily identical) degree, which will be nearly independent of the vulcanization reaction, provided that the black does not interfere with the latter. This is not to say that the chemical nature of polymer, filler and cross-linking reaction are not important variables in reinforcement, but the specific effects they produce are differences in degree and not in kind. 

For carbon-black fillers, structure, particle size, particle porosity, and overall physico-chemical nature of particle surface are important factors in deciding cure rate and degree of reinforcement attainable. The pH of the carbon black has a profound influence. Acidic blacks (channel blacks) tend to retard the curing process while alkaline blacks (furnace blacks) produce a rate-enhancing effect in relation to curing, and may even give rise to scorching. 

Another important factor is the particle size of the carbon black filler. The smaller the particle size, the higher the reinforcement, but the poorer the processability because of the longer time needed for dispersion and the greater heat produced during mixing. Blacks of the smallest particle size are thus unsuitable for use in rubber compounding. 

Sample used in reference (14) is Viton A, cross-linked and reinforced with carbon black filler. The description of the cross-linking method is given in detail in the same reference. 

Figure 10.25. Tensile strength data for Kraton 101 (SBS triblock polymer) ( ) compared with those for an SBR vulcanizate containing 25% by volume of 350-A polystyrene latex spheres (O) (Morton and Healy, 1968) and SBR vulcanizate reinforced with 30% by weight HAF carbon black filler ( ). (Morton and Healy, 1968 Smith, 1970.)...

Carbon black masterbatch 3.06 Carbon black (30%) reinforcing filler... 

Rather peculiar to the rubber industry is the use of the fine particle size reinforcing fillers, particularly carbon black. Fillers may be used from 50 phr to as high as 100-120 phr or even higher proportions. Their use improves such properties as modulus, tear strength, abrasion resistance, and hardness. They are essential with amorphous rubbers such as SBR and polybutadiene that has little strength without them. They are less essential with strain-crystallizing rubbers such as NR for many applications but are important in the manufacture of tires and related products. 

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