Silica carbon black, effect

Reinforcements are used to enhance the mechanical properties of a plastic or elastomer. Finely divided silica, carbon black, talc, mica, and calcium carbonate, as well as short fibers of a variety of materials, can be incorporated as particulate fillers. Incorporating large amounts of particulate filler during the making of plastics such as polypropylene and polyethylene can increase their stiffness. The effect is less dramatic when temperature is below the polymer s Tg. 

Nonblack fillers such as the precipitated silicas can reduce both rate and state of cure because of their strong physical interactions with the polar activator and accelerator chemicals. Neutral fillers such as calcium carbonate (whiting) and clays have little or no effect on the cure properties. Carbon black effects are small. 

Similar results were obtained for mixtures of polyurethane and PVC and poly(e-caprolactone) with styrene-acrylonitrile copolymer. It was found that fillers (silica, carbon black, and talc) broaden the rubbery PU transition, shifting it to higher temperatures. This effect was found to be less pronounced for the high temperature PVC relaxation. The positions of the relaxation maxima are shifted... 

For equivalent particle size the carbon blacks are the most powerful reinforcing fillers. However, fine particle size silicas can be very useful in non-black compounds whilst other fillers such as aluminium hydroxide, zinc oxide and calcium silicate have some reinforcing effect. 

Exfoliating layered particles such as the clays, mica, or graphite is being used to provide very effective reinforcement of elastomers at loading levels much smaller than in the case of solid particles such as carbon black and silica [228-231]. Other properties can also be substantially improved, including increased resistance to solvents, and reduced permeability and flammability. 

Behymer and Hites (1985) determined the effect of different substrates on the rate of photooxidation of acenaphthylene using a rotary photoreactor equipped with a 450-W medium pressure mercury lamp X = 300-410 nm). The photolytic half-lives of acenaphthylene absorbed onto silica gel, alumina, fly ash, and carbon black were 0.7, 2.2, 44, and 170 h, respectively. 

Since carbon black and amorphous silica tend to form clusters of spheres (grasping effect), an additional modification of the Einstein equation was made to account for the nonspherical shape or aspect ratio (L/D). This factor (/) is equal to the ratio of length (L) to diameter (D) of the nonspherical particles (/= L/D). 

Filler, in general, can be defined as finely divided particles that are often used to enhance the performance and various desirable properties of the host matrix, depending on a typical application. A great deal of research endeavors have been dedicated to the development and the use of different fillers with a dimension at the nanometer level. In rubber technology the term nano is not unfamiliar to a rubber specialist. Since the start of the twentieth century, carbon black and silica have been utilized as effective reinforcing agents in various rubber formulations for a variety of applications. The primary particle sizes of these fillers remain in the nanometer range. However, with these conventional fillers the dispersion toward individual... 

Application of a plasma coating onto carbon black is very difficult compared to silica. It was only practically feasible for fullerene soot (left over from the fullerene production), which contains a large amount of reactive groups on its surface. Polyacetylene-plasma-treated fullerene soot provides an improved dispersion in SBR and in a SBR/EPDM blend compared to untreated fullerene black. However, the effect on the stress-strain properties is rather limited and the coating has only a slight effect on the final properties. 

In some instances, combinations of Cig and silica columns are also used for better purification of the crude extracts (431, 445). A combination of Cg, silica, and amino solid-phase extraction columns has been successfully employed to fractionate anabolic and catabolic steroid hormone residues from meat in polar and nonpolar neutral and phenolic compounds, and to purify further each fraction effectively (452). Another combination of two solid-phase extraction columns, one using a graphitized carbon black sorbent and the other Amberlite resin in the hydroxyl form, allowed neutral anabolics to be isolated and separated from acidic anabolics and their metabolites (453). A combination of basic alumina column placed in tandem with an ion-exchange column has also been applied for the purification of the crude extracts in the determination of diethylstilbestrol and zeranol (427), and estradiol and zeranol in tissues (450). 

The mobility in both tightly and loosely bound BR and isoprene rubbers increases, and the fraction of bound rubber decreases with a decreasing concentration of silanol groups on the silica surface [124], This led to the suggestion that the silanol groups on the silica surface are active sites for the chain adsorption. The grafting of aliphatic chains to the silica surface leads to a decrease in BR-silica interactions [125]. The effect is less pronounced in BR filled with carbon black containing aliphatic chains at the surface. 

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