INVESTIGATION OF THE EFFECTS OF DEGRADATION OF HIGH DENSITY POLYETHYLENE BY 13C NMR SPECTROSCOPY AND &#x00BH; RELAXOMETRY.

The structural and dynamic changes occurring in high-density polyethylene exposed to gamma-, X-radiation and extreme temperature have been investigated by high-resolution solid state CP/MAS ¹³C NMR and ¹H NMR relaxometry. The ¹³C CP/MAS NMR spectra show that the gamma and X-radiation can induce the formation of Y-type branches in HDPE. The Laplace distribution of transverse T₂ and longitudinal T₁ relaxation times are used first to identify dynamics and morphological components of HDPE samples and then to characterize the degradation effects of these samples subjected to external aging factors. The small amplitude of the fourth component from T₂ Laplace spectra confirms the connection of free ends of polymer chains to form Y-branches HDPE subjected to X-radiation. The T₁ spectra Laplace show that the cooling at nitrogen temperature will affect mostly the crystallinity of HDPE. [ABSTRACT FROM AUTHOR]