Effects of non entangled chains

Rg being the radius of gyration and Na the Avc dro s number it follows that  

The temperature dependence of T o is mainly included in the fnction coefficient (relation 5-22). Therefore, qo can be expressed by  

The plot of a master curve of the thermal variations of rio for various molecular weights and temperatmes (Fig. 23) shows that the expansion coefficient Uf can be considered as a constant in a wide range of temperatures. The vertical and horizontal shift factors respectively describe the mass dependence of the radius of gyration and temperature T . 

The variations of are derived from the horizontal shift factor and can be expressed by (Fig. 24)  

For polystyrene, D = 83 SOOg.mol i, which means that beyond a mass of approximately D, the temperature T is fixed - (T ) = 49.7 0.3°C.Therefore, in the entangled region, the free volume fraction is constant at a given temperature and the iso-free volume state merges into the isothermal state. 

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