THE EFFECT OF ANNEALING ON STRETCHED TRANS-1,4-POLYISOPRENE NETWORKS

Variations of stress with temperature for stretched networks of trans-polyisoprene networks in the crystallization region are reported. Such profiles are characteristically U-shaped with the stress at lower temperatures often climbing to high levels. Valley widths of the profiles narrow as annealing temperature increases to about 50-degrees-C, then widen at yet higher temperatures. The degree of crystallization at 22-degrees-C is 37% and independent of deformation and annealing temperature. The beta crystal form is overwhelmingly present with traces of other crystal forms appearing only at high deformations. The theory of stress-induced crystallization provides a good description of experimental results provided the nucleation parameter sigma is dependent upon deformation. Therefore, the data provide good qualitative support for the theory in its current form.