Abstract: Crosslink structures, photolytic products of benzophenone(BP) as a photoinitiator and their formation mechanisms in BP-photoinitiated crosslinking of low density polyethylene (LDPE) and its model compounds have been studled by solution state high resolution₁₃C NMRand fluorescence spectroscopy etc..Both H-links and Y--type long branches in the photocrosslinked LDPE (XLPE) have been ohserved and identified for the first time.The concentrations of H- and Y-type crosslinks are estimated to be 5.7～16.9 and 7.6～21.6 structure units per 10000 carbon atoms with the XLPEsamples UV-irracliated for 5～10 seconds in the melt, respectively.The main photolytic product of BPidentified is benzopinacol.There are indications that a small amount of a-alkylbenzhydrols are also possibly formed by the reactions of ketyl radicals with alkyl radicals.

Key words: Low density polyethylene (LDPE), Benzophenone, Crosslink structure, Photolytic products, Photocrosslinking mechanism