is stress
is the change in Helmholtz Free Energy
- Helmholtz Free Energy is defined by F = U - TS and contrasts with Gibbs Free Energy in that Gibbs free energy constrains pressure to a constant, but Helmholtz constrains volume to a constant.
is the change in the extension
ratio
is the extension ratio [Sperling-389]
is
temperature
is volume
the variable 
is
the number of polymer chains.
this is a different 'n' than the 'n' from PV=nRT!
is the
Real Gas Constant
is the length when a stress is applied
to the elastomer.
is the length when no stress is
applied.
