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REACTION MECHANISM OF BENZOPHENONE-PHOTOINITIATED CROSSLINKING OF POLYETHYLENE
作者姓名:Bao-jun  Qu  State  Key  Laboratory  of  Fire  Science  and
基金项目:The project was successively supported by the National Natural Science Foundation of China (No. 50073022, No 59773030, No. 59543002 and No. 5880104).
摘    要:The radical intermediates, the crosslink microstructures, and the reaction mechanism of benzophenone (BP)-photoinitiated crosslinking of low-density polyethylene (LDPE) and model compounds (MD) have been reviewed in detail.The spin-trapping electron spin resonance (ESR) spectra obtained from the LDPE/BP systems with spin-trap agents showthat two kinds of polymer radical intermediates are mainly formed: tertiary carbon and secondary carbon radicals. The spin-trapping ESR studies of MD/BP systems give further evidence that photocrosslinking reactions of PE predominantly takeplace at sites of tertiary carbon, secondary carbon, and especially allylic carbon when available. The high resolution ~(13)C-NMR spectra obtained from LDPE and MD systems show that the crosslink microstructures have H- and Y-type links andthat their concentrations are of the same order. The fluorescence, ESR ~(13)C and ~1H-NMR spectra from the PE and MDsystems demonstrate that the main photoreduction product of BP(PPB) is benzpinacol formed by the recombination of twodiphenylhydroxymethyl (K·) radical intermediates. Two new PPB products: an isomer of benzpinacol with quinoid structure,1-phenylhydroxymethylene-4-diphenylhydroxymethyl-2, 5-cyclohexadiene and three kinds of α-alkyl-benzhydrols have beendetected and identified. These results provide new experimental evidence for elucidating the reaction mechanism in the BP-photoinitiated crosslinking of polyethylene.

收稿时间:2001-08-06
修稿时间:2001-09-07

REACTION MECHANISM OF BENZOPHENONE -PHOTOINITIATED CROSSLINKING OF POLYETHYLENE*
Bao-jun Qu State Key Laboratory of Fire Science and.REACTION MECHANISM OF BENZOPHENONE-PHOTOINITIATED CROSSLINKING OF POLYETHYLENE[J].Chinese Journal of Polymer Science,2002,0(4):291-307.
Authors:Bao-jun Qu
Institution:Bao-jun Qu State Key Laboratory of Fire Science and Department of Polymer Science and Engineering University of Science and Technology of China Hefei 230026 China
Abstract: The radical intermediates, the crosslink microstructures, and the reaction mechanism of benzophenone (BP)-photoinitiated crosslinking of low-density polyethylene (LDPE) and model compounds (MD) have been reviewed in detail.The spin-trapping electron spin resonance (ESR) spectra obtained from the LDPE/BP systems with spin-trap agents showthat two kinds of polymer radical intermediates are mainly formed: tertiary carbon and secondary carbon radicals. The spin-trapping ESR studies of MD/BP systems give further evidence that photocrosslinking reactions of PE predominantly take place at sites of tertiary carbon,secondary carbon,and especially allylic carbon when available.The high resolution 13C-NMR spectra obtained from LDPE and MD systems show that the crosslink microstructures have H-and Y-type links and that their concentrations are of the same order.The fluorescence,ESR,13C and 1H-NMR spectra from the PE and MD systems demonstrate that the main photoreduction product of BP(PPB) is benzpinacol formed by the recombination of two diphenylhydroxymethyl(K·)radical intermediates.Two new PPB products:an isomer of benzpinacol with quinoid structure,1-phenylhydroxymethylene-4-diphenylhydroxymethyl-2,5-cyclohexadiene and three kinds of α-alkyl-benzhydrols have been detected and identified.These results provide new experimental evidence for elucidating the reaction mechanism in the BP-hotoinitiated crosslinking of polyethylene.
Keywords:Photocrosslinking mechanism  Polymer radical intermediates  Crosslink microstructures  Photolytic products of benzophenone  Polyethylene  Model compound
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