摘要
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。
Radical intermediates formed by UV-irradiation of low density polyethylene ( LDPE) in the presence of benzophenone (BP) as a photoinitiator have been trapped by using 2,4,6-tri-t-butylnitrosobenzene (BNB) as a spin -trapping reagent. The resulting spin-adduct radicals have been characterized in situ by ESR spectroscopy. Two kinds of spin-adducts are detected and identified : a tertiary carbon radical and a secondary carbon radical which are formed by addition of the spin-trap (BNB) to two polymer radicals. These intermediates are produced by hydrogen abstraction of the BP excited triplet state from branch points and methylene groups of the LDPE chain, respectively. This is the evidence that the photocrosslinking of LDPE mainly takes place at both tertiary carbons (branch points ) and secondary carbons along the chains and that H-shaped links dominate. Secondary bonded hydrogens are less reactive but occur in much larger number than tertiary bonded hydrogens in LDPE.
出处
《波谱学杂志》
CAS
CSCD
1993年第1期1-8,共8页
Chinese Journal of Magnetic Resonance
基金
The Project Supported by National Natural Science Foundation of China
关键词
ESR
聚乙烯
交联
Electron spin resonance
Radical intermediates
Spin trapping
Low density polyethylene
UV irradiation .
