Constituents of the Drawing Stress

The stress arising during stretching a semicrystalline polymer thus is set up of three contributions  

An evaluation of experimental data on the basis of the rheomechanical model depicted in Fig. 10.18 allows their determination. In the zero strain rate limit, where all viscous forces vanish, one finds a superposition of the network force with a force that is transmitted by the crystal skeleton. The model describes 

This suggests describing the viscous force by the Eyring law of viscosities 

In the limit ep 0 the Eyring law turns into the Newton law, with 

The Eyring law of viscosity uses two parameters, the reference stress to and the reference strain rate eo, rather than one viscosity coefficient rjo only. According to Eq. (10.8) r]o, uo and eo are related by 

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