Extension of the Flory-Rehner Theory of Swelling to an Anisotropic Polymer System

The Flory-Reimer theory for isotropic swelling of rubber crosslinked in the dry state is extended to an anisotropic system crosslinked in the dry, oriented state. The new parameters introduced into the equation can be readily determined from dimensional changes of the fiber in a suitable solvent using a photomicrographic technique. Unlike other methods, such as the cathetometric and weight methods, this technique enables the attainment of swelling equilibrium usually within 30 minutes. Good agreement is obtained between the equivalents of crosslinks calculated from chemical analyses and from swelling measurements, respectively.