Abstract
Dynamic mechanical loss of solution-grown polyethylene crystals is measured by the suspension method as a function of temperature and the crystalline dispersion (α dispersion) is observed above 40°C in just the same manner as in melt-grown polyethylene. In the temperature range of this dispersion, the ratio of crystal lattice constants b/a progressively changes toward that of a higher symmetry hexagonal form with increasing temperature. NMR line width of the broad component becomes gradually narrow with rising temperature in this temperature range. It is concluded from these reasons that the α dispersion of polyethylene should be ascribed to the rotational vibration of chain molecules in crystalline phase about c-axis. Similar behavior of low molecular weight paraffin crystals below the rotational transition point affords an additional confirmation of the above conclusion. Crystalline dispersions of other polymers are briefly discussed.