Two Lifshitz points in melt-crystallized polymers: nanostructure, necking, energy dissipation

TL;DR

This paper presents a scaling theory model for melt-crystallized polymers, identifying two Lifshitz points and linking structural, energetic, and dynamic properties with phase transition phenomena, validated by experimental data.

Contribution

It introduces a novel model incorporating two Lifshitz points in polymers, connecting phase transition theory with polymer nanostructure and energy dissipation.

Findings

Model estimates secondary relaxation transition temperatures.

Good agreement with experimental data on polymer structure.

Identifies two Lifshitz points influencing polymer properties.

Abstract

In frameworks of scaling theory of phase transitions and critical phenomena the structure of melt-crystallized polymers is discussed. The model constructed follows drawing polymeric materials and dissipating the energy during the transition from isotropic to oriented state. It is possible to estimate temperatures of secondary relaxation transitions. The entropic parameters of the model are: the space dimension; the number of components of an ordering field; the polymerization degree. The Kuhn segment, the melting temperature and the difference of energies of two rotating isomers can be regarded as energetic parameters. The model enables to calculate a number of important structural and dynamic physical values: the density ratio of crystalline to amorphous phase; the thicknesses of crystalline and amorphous layers in an isotropic lamellar material; the crystallinity degree; the fluctuation spacing due to entanglements; the neck draw ratio; the draw ratio at break; the elastic deformation connected with gosh-trans transitions; etc. This model is based on the assumption that there are exist two Lifshitz points in such polymers. The neck draw ratio characterizes an irreversible process during which the energy dissipation is observed. It is the main difference from magnetic systems, for example. The results obtained are in a good agreement with experimental data including the results found for solution-crystallized polymers.