Abstract: H-type cross-links produced by photoinitiated cross一linking of n-C₂₄H₅₀ as a model compound of polyethylene in the presence of benzophenone as photoinitiator have been studied for the first time by solution-state ¹³C NMR spectroscopy.Resonance lines assigned to the CH,α-CH₂,and β-CH₂ carbons associated with H-type cross-links have been observed and identified for the photocross-linked samples,and compared with data from the model compound and γ-irradiation cross-linking of n-paraffins and polyethylene.A new resonance line at 40.83 ppm is attributed to methine carbons in H-links.The other two new resonances at 31.57 ppm and 28.37 ppm are assigned to α-CH₂ and β-CH₂,respectively.The quantitative studies in this work show that the number of H-links is estimated to be 8.5-11.0 per 10000 carbon atoms for samples UV-irradiated in vacuum in the melt for 3-5min.

Key words: ¹³C NMR, UV irradiation, Paraffin, Model compound, Cross-links