Dynamic-mechanical and nuclear magnetic resonance study of relaxation processes in ultra-high molecular weight polyethylene fibres

Abstract

The relaxation processes (α, β, and γ) in UHMW PE fibres drawn to different draw ratios λ have been studied by dynamic-mechanical and nuclear magnetic resonance methods. The temperature dependences of tensile loss moduli E″ and spin-lattice relaxation times T1 have been analyzed assuming distribution of correlation times τ according to the Davidson—Cole function. The activation energies Ea and parameters e characterizing widths of distribution, and asymptotic value τ0 for correlation times have been determined from experimental data for low-temperature γ-process and for high-temperature α-process. A weak β-process has been found by dynamic-mechanical method and quantitative analysis was made only for fibres with λ = 9. The temperature dependences of second moment M2 of the broad-line NMR spectra have been analyzed according to the Gutowsky—Pake formula, which includes only a single correlation time τc without distribution. In this case the activation energies Ea and values of τ0 have been determined.