Vulcanization of Rubber and Swelling Equilibrium

Noting that the total volume of the swollen rubber is the sum of the polymer and solvent volumes, we have 

Combining the two previous equations and recalling the definition of the fi ee-energy change on mixing, we find that 

Differentiating Eq. (10.8.3) with respect to n, and using the results of Eq. (9.3.30) gives the solvent chemical potential as 

At phase equilibrium between the swollen rubber and the piue solvent, must equal gi, so that 

Example 10.5 Estimate a value for the ehain density in units of moles per cubic centimeter for butyl rubber if the equilibrimn swelling ratio, q, in cyclohexane is 8. Here, the swelling ratio is defined as the ratio of the equilibrium swollen volume to the original unswollen volume. In accordance with the data of Flory [15], let be 0.3. The molar volume of cyclohexane is 105 cm.  

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