Diffusivity of Low Molecular Weight Components in Molten Polymers

5 DIFFUSIVITY OF LOW MOLECULAR WEIGHT COMPONENTS IN MOLTEN POLYMERS 

This model, based on the earlier work of Fujita (18), currently appears to be the most effective theory to describe diffusion both above and below Tg. It adopts the notion that all transport processes are governed by the availability of free volume in the system. Free volume is a useful concept representing a specific volume V/v present as holes of the order of molecular (monomeric) dimensions or smaller, which together with the specific volume of the molecules themselves, Vo, gives the total specific volume, V 

As the temperature above Tg decreases, the kinetic energy of chain segments decreases as well and the volume contracts, sharply reducing the relative amount of free 

---

Diffusivity of Low Molecular Weight Components in Molten Polymers, 420... 

---