RELATIONSHIP BETWEEN MELTING THERMODYNAMICS AND STRENGTH FOR ULTRADRAWN POLYMERS

With the help of DSC, WAXS, and SAXS techniques highly oriented PE sam ples produced in six different ways in the range of draw ratios from 2 5 up to 300 have been investigated. The decrease of melting interval u p to zero and the significant increase of melting temperature up to it s equilibrium value are observed with draw ratio. The analysis of DSC data enabled us to calculate the thermodynamical parameter of intracha in cooperativity of melting which was found to be equal to nu almost-e qual-to 2 x 10(3) nm. Although the observed thermodynamical characteri stics corresponded to those expected for hypothetical macroscopic sing le crystals of PE, the combining of DSC and X-ray data allow to consid er ultraoriented PE as consisting almost entirely of very extended (up to nu almost-equal-to 2 x 10(3) nm) straightened chain sections, each of which going through dozens of small crystallites and intercrystall ine regions containing defects of disclinational type. As a result, th e linear correlation between the parameter nu and the mechanical stren gth sigma of oriented PE has been revealed.