Solvent effects, carbon black

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. 

Schick and Harvey (49) summarize an interesting investigation of the effect of the choice of solvent on the conformation of a polymer adsorbed at the solution interface with Spheron 6 carbon black. A noteworthy conclusion concerns the occurrence of extended and looped configurations of the adsorbed polymer molecules formed from good or poor solvents, respectively. 

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. 

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. 

In addition to, or instead of, polystyrene and oils, polymers such as polypropylene, polyethylene, or ethylene-vinyl acetate copolymer can be blended with these block copolymers. Blends with S-B-S or (S-B) -X block polymers usually show greatly improved ozone resistance (S-EB-S already has excellent ozone resistance). In addition, these blends have some solvent resistance. In certain cases, some oils that are stable to UV radiation reduce the stability of the blends however, the effects can be minimized by the use of UV stabilizers and absorptive or reflective pigments (e.g., carbon black or titanium dioxide). 

Stress-softening in moderately loaded black vulcanizates increases with time and recovers (partly) with time. The first effect becomes more pronounced as temperature falls and the second effect more rapid in the presence of solvents and at higher temperatures. At temperatures near the glass transition, carbon black reinforces SBR very little indeed. 

SEM / mechanical properties / DMA / carbon black filler (0-25 phr) / effects of mixing sequence internal mixer at 150°C / mechanical properties / DMA / solvent swelling / effects of adding ZnO or ZnSt to form ionomeric network / DSC / FTIR / UV / SEM internal mixer at 180°C /mechanical and thermal properties / ETIR... 

Graphitized carbon black (GCB) has been reported to be a highly effective sorbent for sample clean-up but also removes structurally planar analytes, limiting its applications. Addition of HOAc to the extraction solvent may help to improve recovery of analytes, but it also inhibits the retention of acidic matrix compounds. Several papers have reported the use of Cl8 for dSPE in veterinary residue analysis. " The use of PSA, NH2, and silica has also been reported. While dSPE does not provide the same degree of clean-up as SPE, it does provide good recovery and reproducibility, coupled with practical and cost advantages. ... 

Organic impurities are mainly polyaromatic hydrocarbons (PAHs) (Taylor et al., 1980). They correspond to partially unconverted fuel that has been readsorbed onto carbon black. These PAHs are present at a very low content and, because of their firm adsorption on carbon black, the extraction must be conducted in a Soxhlet apparatus with a strong solvent (toluene) and at high temperature (80°C). However, it has been demonstrated that organic impurities have no significant effect on carbon black reinforcement (Custodero et al., 1992). 

Nishi, T., Effect of solvent and carbon black species on the rubber-carbon black interactions studied by pulsed NMR, J. Polym. ScL, B12, 685-693 (1974). 

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