A simplified model for a network structure of the fiberforming substance has been proposed, and relation between the mechanical properties and draw ratio has been investigated. It hasbeen assumed that the mechanical properties are principally determined by the orientationdegree, and that the influences of crystallization and other internal energy changes can beneglected comparing with this orientation effect. From the consideration of the model followingresults are obtained: Young's modulus (
E) increases with increasing draw ratio, and itsasymptotic upper limit is (5
E0), where
E0 is Young's modulus of the isotropic body. On theother hand torsional modulus (
n) decreases with increasing draw ratio. The completely orientedamorphous polymer exhibits zero torsional modulus, The ratio (
E/3
n) is unity only for aisotropic material with a Poisson's ratio of 1/2. Finaly this results are compared with themechanical properties of Nylon and Polyethylene Terephthalate which were observed.
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