Modeling the Viscoelastic Behavior of Crystalline Polymers

The viscoelastic properties of the crystalline zones are significantly different from those of the amorphous phase, and consequently semicrystalline polymers may be considered to be made up of two phases each with its own viscoelastic properties. The best known model to study the viscoelastic behavior of polymers was developed for copolymers as ABS (acrylonitrile-butadiene-styrene triblock copolymer). In this system, spheres of rubber are immersed in a glassy matrix. Two cases can be considered. If the stress is uniform in a polyphase, the contribution of the phases to the complex tensile compliance should be additive. However, if the strain is uniform, then the contribution of the polyphases to the complex modulus is additive. The 

The theory of two potential wells of nearly equal depth has been used to explain secondary relaxations in amorphous polymers. Recent results by L. C. E. Struik led to the result 

After derivation with respect to the temperature and subsequent rearrangements, we obtain 

Note that for weak relaxation, where G /Gqo is close to unity, 

These results indicate that the relaxation strength decreases with increasing temperature. 

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