Cross-link Density of Rubber by Swelling to Equilibrium

APPENDIX 9.3 DETERMINATION OF THE CROSS-LINK DENSITY OF RUBBER BY SWELLING TO EQUILIBRIUM  

The present experiment is based on the rapid swelling of elastomers by organic solvents. Application of the Flory-Rehner equation yields the number of active network chain segments per unit volume, a measure of the extent of vulcanization (C1,C2). 

Time About 1 hour Level Physical Chemistry Principles Illustrated  

One long tweezers to remove swollen rubber band Paper towels to blot wet swollen rubber band 

The rubber band swells to about twice its original length, but then it remains stable. Note that swelling to twice its length means a volume increase of about a factor of 8. Also, note that the swollen rubber band is much weaker than the dry material and may break if not treated gently. 

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