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    STUDIA CHEMIA - Issue no. 3 / 2011  
         
  Article:   INVESTIGATION OF THE EFFECTS OF DEGRADATION OF HIGH DENSITY POLYETHYLENE BY 13C NMR SPECTROSCOPY AND 1H RELAXOMETRY.

Authors:  DUMITRIȚA MOLDOVAN, MIHAELA POPA, RADU FECHETE, ANNE BAUDOUINE, MIHAI TODICA. 		 
       
         
  Abstract:  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.

Keywords: High Density Polyethylene (HDPE), gamma and X-ray irradiation, 13C CP/MAS NMR, 1H NMR, T1, T2, Laplace distributions 		 
         
     
         
         
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