DRAWING-INDUCED CHANGES IN THE PROPERTIES OF POLYETHYLENE FIBERS PREPARED BY GELATION CRYSTALLIZATION

Fibers of ultrahigh molecular weight polyethylene were prepared by drawing dry specimens obtained by gelation/crystallization from solution. The maximum draw ratio ( lambda ) attained was 250. The properties of the fibers were assessed by measurements of density, birefringence, differential scanning calorimetry, infrared dichroism, sonic velocity, and dynamic modulus. The results have been analyzed in terms of a two-phase model of crystalline and amorphous regions. All properties approach a limiting value at a draw ratio of about 100. The degree of crystallinity and melting point decrease initially (for lambda less than 12) and then increase rapidly with lambda up to their limiting values.