Bound rubber extraction time

According to a JSR patent Nd-catalysis allows for the polymerization of BD in the presence of carbon black. By this method a BR/carbon black master batch is obtained. The master batch technology eliminates time and energy consuming mixing of carbon black and rubber [340,341]. According to this patent the content of bound rubber (amount of rubber which can be extracted from a carbon black/rubber mixture with an appropriate solvent, e.g. toluene) is increased and vulcanizate properties are improved. 

In laboratory practice, a small sample of rubber is extracted with solvent (usually toluene) at room temperature for a specified period of time (1 week) and the percentage of bound rubber, Rb, is calculated from the equation ... 

Proton spin resonance measurements on carbon black filled rubbers confirm the relatively small effect of the black on local segmental mobility. Waldrop and Kraus (107) were unable to find evidence for two spin-lattice relaxation times (one for surface rubber and one for bulk rubber) and found very little effect of carbon blacks on the position of the minimum in the spin-lattice relaxation time (7j) vs. temperature curve. The shape of the curve was also substantially unaffected (107). Extraction of free rubber from an uncross-linked SBR-HAF black mix did not accentuate the effect of the carbon black. More recently Kaufmann, Slichter and Davis (108) reported the observation of two spin-spin relaxation times (T2) in the bound rubber phases of polybutadiene and ethylene-propylene rubber, each reinforced with 50 phr of an SAF black (155 m2/g surface area). The amount of fully immobilized polymer was only 4% of the total, but the remainder of the bound rubber displayed... 

The mass mi corresponds to the rubber compound before extracting, and it is the sum of the mass of the bonded rubber part Rf the mass of the soluble rubber part and filler, m2 is the mass of the rubber-filler gel, which is the sum of the bonded rubber part and filler, is the mass concentration of filler in the single rubber mixture or binary blends. 1 is the mixing time in an internal mixer. The difference between the terms rubber layer L and bound rubber, which has been commonly used in rubber technology, was discussed in our previous work. To understand the physical background of the rubber layer L, we correlated the wetting behaviour determined from our extraction experiment with the infiltration behaviour reported in the literature." In a capillary flow of a Newtonian fluid in a small gap between two parallel plates, the position x of the liquid-air interface at time t is given by Equation (6.27) ... 

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