Carbon black silica when compared

Silica is unique among nonblack fillers. Its reinforcing ability is comparable to that of carbon black, especially when mixed with a suitable coupling agent, and its transparency affords many products. Additionally, it is chemically synthesized, which means that a wide range of silica (in terms of diameter, surface area, or surface activity) may be produced depending on the reaction routes and reaction conditions. 

Some materials, among the most porous, show a large volume variation due to mechanical compaction when submitted to mercury porosimetry. High dispersive precipitated silica shows, as low density xerogels and carbon black previously experimented, two successive volume variation mechanisms, compaction and intrusion. The position of the transition point between the two mechanisms allows to compute the buckling constant used to determine the pore size distribution in the compaction part of the experiment. The mercury porosimetry data of a high dispersive precipitated silica sample wrapped in a tight membrane are compared with the data obtained with the same sample without memlM ane. Both experiments interpreted by equations appropriate to the mechanisms lead to the same pore size distribution. 

SBR filled with intercalated montmorillonite had substantially lower toluene uptake compared with the same rubber filled with carbon black (see Figure 15.42). Figure 5.28 shows that the diffusion coefficient of kerosene, which defines penetration rate, decreases when the concentration of carbon black in SBR vulcanizates is increased. Figure 15.33 compares the uptake rate of benzene by unfilled rubber and by silica and carbon black filled rubber. Both fillers reduce the solvent uptake but carbon black is more effective. 

When the behavior of carbon black and silica is compared in compounded rubber, it is evident that silica adsorbs less rubber than carbon black. In addition to the differences in the chemical compositions of the surfaces this difference is caused by the differences in the dispersive components of surface energies of each filler. Car-... 

Silica-filled systems will produce higher viscosity compounds when compared to the use of carbon black although this effect can be moderated through the use of silane coupling agents. The mixing process with silanes must be very well controlled to avoid wide fluctuations in processing and end component properties. 

Most of the specific properties of silica (and silicates) were known more than three decades ago, as reviewed by Wagner in 1976, who somewhat foresaw the tremendous developments that followed. Indeed, in the last decades, significant progress was made in using silica in diene elastomers, supported by the peculiar dynamic properties this filler brings to (diene) elastomers. It permitted the development of the so-called "green tire," because a lower rolling resistance is obtained, when compared with carbon black reinforced tires. 

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