Radiation degradation of linear low density polyethylene: Determination of lamellae thickness, crystallinity and crosslinking by solid-state 13C NMR and DSC

Solid-state C NMR has been used to study changes in the crystallinity of linear-low-density polyethylene during γ irradiation. NMR intensities and DSC fusion enthalpies showed that the crystalline content decreased above 2 MGy. NMR relaxation times, T(H), have been used to follow the decrease in thickness of the crystallites. The first quantitative observation of H-crosslinks in irradiated polyethylene by solid-state NMR is reported. The value of G(X)=3.7 is considerably higher than the range of values reported from soluble fraction analysis and suggests a non-uniform spatial distribution of crosslinks