Elastic Behavior of a Rubber Band

The gelation molecule is basically composed of short a-hehcal segments in the form of a triple helix with numerous intramolecular bonds at room temperature see Section 9.13. The a-helical segments are interrupted by prohne and hydroxy proline functional groups. These groups disrupt the helical structure, yielding intervening portions of chain that behave hke random coUs, and which may be relatively free to develop intermolecular bonds. The subject has been reviewed by Djabourov (A7) and Mel nichenko et al. (A8). 

In this experiment the concentration of sugar was kept constant so as to minimize its effect on the modulus. In concluding, it must be pointed out that if sanitary measures are maintained, the final product may be eaten at the end of the experiment. If gelation five times normal or higher is included in the study, the student should be prepared for his or her jaws springing open after biting down  

Macromolecular Chemistry of Gelatin, Academic Press, Orlando, 1964. A2. E. M. Marks, in Encyclopedia of Chemical Technology, Kirk-Othmer, Interscience, New York, 1966, Vol. 10, p. 499. 

Sperling, Interpenetrating Polymer Networks and Related Materials, Plennm Press, New York, 1981, p. 177. 

Stretching a rubber band makes a good demonstration of the stress-strain relationships of cross-linked elastomers. The time required is about 30 minutes. 

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Figure A9.2.1 Simple rubber-elastic behavior of a rubber band under increasing load.

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