Some morphological factors in thermomechanical analysis of crystalline polymers

Morphological factors exerting an effect on thermomechanical analyses of crystalline polymers are discussed for three kinds of samples with quite different morphologies. (1) Bulk-crystallized linear polyethylene (PE) with spherulitic structure shows an a absorption, which was shown to be composed of two absorptions, α1 and α2. Based on the super-structural characterization and viscoelastic behavior of a single crystal mat of PE, the α1 absorption was assigned to the deformation associated with mosaic block boundaries and the α2 absorption to the uniform shear deformation of lamellar crystals. (2) Highly oriented and well crystallized poly-[p-(2-hydroxyethoxy)benzoic acid] shows the α → β crystal transformation caused by drawing stress. The role of tie links translating the stress along the fiber axis was proved by calculating the mechanical dispersion behavior of the dynamic modulus based on the super-structural parameters. (3) Oriented crystallites of PE prepared from dilute solution with a shish-kebab morphology shows outstanding thermal stability in comparison with lamellar crystals as found in melt-spun and drawn fibers and solid-state extrudates of PE. The TMA data were compared with DSC thermograms.