Melting Temperature and Change of Lamellar Thickness with Time for Bulk Polyethylene

The melting tempera ture of linear polyethylene has been obtained as a function of the t ime and tempera ture of crystallization. Recrystallization was minimized by a special melting procedure. By interpreting the melting points as characteristic of a given lamellar thickness, i t was found t h a t the thickness of crystals of appreciable age increased linearly with t he logari thm of their t ime of existence. The lowest melting (i.e., thinnest) lamellae in a given specimen may be assumed to have either existed for only a short period of t ime, or to have been impeded in their growth in the chain direction, and they were found to have an es t imated thickness close to t h a t predicted by recent kinetic theories of polymer crystal growth wi th chain folding.