Orientation of polymer molecules during melt spinning. I. Estimation of degree of orientation by retraction above Tm

Abstract

AbstractThe elastic deformation ratio by spin‐stretching was estimated by means of thermal retraction technique, data for a melt‐spun filament from a crystalline polymer were compared with those from an amorphous one. The necessary conditions for equilibrium retraction were determined as 7 min at 170°C for amorphous polystyrene and 30 min at 180°C for high‐density polyethylene. The effects of molecular weight and melt draw ratio on the retraction behavior were discussed and concluded to be negligible. The apparent activation energies of viscous flow were calculated from the temperature dependence of the retraction curves. The activation energy for polystyrene decreases with increasing temperature of retraction, as predicted by the WLF equation, and that of polyethylene obeys Arrhenius law (about 12 kcal/mole). This may be attributed to the difference in glass transition temperatures of the two polymers. By measuring the effective melt draw ratio of the resultant filaments of different melt draw ratio, it was made clear that the elastic deformation increases with increasing apparent melt draw ratio. Finally, the optical anisotropy of the filaments was related to the deformation ratio. It was concluded that Kuhn and Grün's equation may be applicable for polystyrene but not for polyethylene.