On the Diffusion Mechanism in Melts of Condensation and Non-Condensation Polymers at High Temperatures
As recently assumed (DOI:10.3144/expresspoly mlett.2019.25), the diffusion mechanism in melts of noncondensation and condensation polymers at high temperatures must be rather different due to the intensive exchange (trans) reactions resulting in dissipation of condensation macromolecules into single repeating units. Considering these peculiarities of condensation polymers, it is concluded that the Reptation concept can be used for explaining the diffusion mechanism of non-condensation polymers (e. g. polyolefins) in the entire temperature interval while for condensation polymers it is applicable only in the range between Tm and approximately (Tm +100)°C. At much higher temperatures, where the exchange reactions are extremely intensive, the diffusion mechanism seems to be the same as in the case of low molecular weight substances.
