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在光引发剂二苯甲酮(BP)存在下,紫外光辐照低密度聚乙烯(LDPE)所形成的自由基中间体已被自旋捕捉剂2,4,6-三特丁基亚硝基苯(BNB)所捕捉,其自旋加合物自由基已为电子自旋共振(ESR)所特征。现已检测和鉴定到二种自旋加合物:一种是叔碳自由基;另一种是仲碳自由基。它们分别是由BP的激发三重态从LDPE链的支化点和亚甲基团上夺氢所形成的自由基中间体同自旋捕捉剂BNB反应生成的。上述的证据表明:LDPE的光引发交联点主要发生在叔碳和仲碳原子上,且H-型交联点占主导地位。
In the presence of photoinitiator benzophenone (BP), free radical intermediates formed by UV irradiation of low density polyethylene (LDPE) have been blocked by the spin trapper 2,4,6-tributylnitroside Benzylbenzene (BNB), whose spin adduct free radicals have been characterized by Electron Spin Resonance (ESR). Has been detected and identified two kinds of spin adducts: one is tertiary carbon free radicals; the other is secondary carbon free radicals. They are generated by the reaction of the excited triplet state of BP with the radical scavenger BNB, which is formed by the radical neutralization of hydrogen on the LDPE chain and methylene groups. The above evidence indicates that the photoinitiated crosslinking sites of LDPE mainly occur on tertiary and secondary carbon atoms, and H-type crosslinking sites dominate.