Application of equivalent model method to dynamic rheo‐optical properties of crystalline polymer

Abstract Assuming that the crystalline polymer consists of the crystalline and the non‐crystalline phase, a mechanical model for the crystalline polymer is constructed. We introduced into this model such complicated circumstances as some parts of the crystalline phase will be largely deformed under a stress concentration and other parts not so much. The temperature dependence of complex moduli of the crystalline polymers with various degrees of crystallinity is illustrated by using the model. On the basis of the model, we have derived an equation for calculating the strain‐optical coefficient of the crystalline polymer from those of the crystalline and the non‐crystalline phase. The equation gives a relation among the rheo‐optical quantities, the viscoelastic quantities and the parameters representing the fine structure and the crystallinity of the polymer. It is concluded from this equation that the strain optical coefficients cannot be expressed by such a simple additive relation as usually employed.