Polymer deformation. III. Annealing of drawn polyethylene single crystals and fibers

Polyethylene single crystals plastically deformed by drawing as much as 100% and fibers that occasionally form during this deformation have been annealed at 121 and 125°C. Striations with a spacing similar to that measured with small‐angle x‐ray diffraction are observed on the fibers in contact with a substrate. No readily apparent change occurs during the annealing of freely suspended fibers. Similar striations are observed along slip bands and other grossly deformed regions within the crystals. Recrystallization through an “ameboid” motion occurs in both drawn and undrawn crystals on Mylar substrates and results in an irregular crystal boundary. The more usual type of recrystallization involving an increase in fold period appears to occur more readily at a given temperature in undrawn crystals than in the plastically deformed ones. The b axis in drawn crystals was found to rotate during the annealing treatment so as to be nearly perpendicular to the draw direction. Any polymer in the monoclinic unit cell returns to the more stable orthorhombic unit cell.