To use all functions of this page, please activate cookies in your browser.

my.chemeurope.com

With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.

- My watch list
- My saved searches
- My saved topics
- My newsletter

## Rubber Elasticity
## Freely-Jointed Chain Model## Additional recommended knowledgePolymers can be modeled as freely jointed chains with one fixed end and one free end (FJC model):
where is the length of a rigid segment, is the number of segments of length , is the distance between the fixed and free ends, and is the "contour length" or . Above the glass transition temperature, the polymer chain oscillates and changes over time. The probability of finding the chain ends a distance apart is given by the following Gaussian distribution: Note that the movement could be backwards or forwards, so the net time average Ideally, the polymer chain's movement is purely entropic (no enthalpic, or heat-related, forces involved). By using the following basic equations for entropy and Helmholtz free energy, we can model the driving force of entropy "pulling" the polymer into an unstretched conformation. Note that the force equation resembles that of a spring: F=kx. ## Worm-Like Chain ModelThe worm-like chain model(WLC) takes the energy required to bend a molecule into account. The variables are the same except that , the persistence length, replaces . Then, the force follows this equation: Therefore, when there is no distance between chain ends (r=0), the force required to do so is zero, and to fully extend the polymer chain (), an infinite force is required, which is intuitive. Graphically, the force begins at the origin and initially increases linearly with . The force then plateaus but eventually increases again and approaches infinity as the chain length approaches ## See also- Elasticity (physics)
- Polymers
- Thermodynamics
Categories: Rubber properties | Thermodynamics |

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Rubber_Elasticity". A list of authors is available in Wikipedia. |