NMR-Studies of semicrystalline polymers using pulse techniques

Abstract

The spin-spin relaxation of protons in polyethylene samples of various crystallinities has been measured using a pulse spectrometer. The magnetisation curves obtained can be decomposed into a series of exponential functions and a (sin a t/ at) · exp (−b t ²) function. The contribution of the latter function to the total magnetisation at t=0 is increasing with increasing crystallinity but is always lower than the crystallinity measured by other methods.

The study of an oxydation series of polyethylene does not show significant differences in the decrease of components of the “amorphous” signal with increasing oxydation time.

The difference between our results and those obtained by resonance methods on the same sample is essentially due to a basic difference in the decomposition method.

The effect of the field modulation on the resonance signal is discussed and a new method for the elimination of this effect is proposed.