Photocrosslinking of polyethylene. I: Photoinitiators, crosslinking agent, and reaction kinetics
Photocrosslinking of polyethylene. I: Photoinitiators, crosslinking agent, and reaction kinetics
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DOI：
10.1002/pola.1989.080271214
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发表时间：
1989-11
期刊：
影响因子：
--
通讯作者：
Y. Chen;B. Rånby
中科院分区：
文献类型：
--
作者：
Y. Chen;B. Rånby
以4-氯二苯甲酮(4-CBP)为光引发剂，氰尿酸三烯丙酯(TAC)为交联剂，在熔体中对高密度聚乙烯进行光交联。研究了影响交联过程的各种因素（使用的光引发剂及其浓度、照射温度和时间、气氛、紫外光源、光强度）。通过优化辐照条件，发现厚度达 2 mm 的样品可以在极短的辐照时间内（约 15 秒）轻松交联至高凝胶含量（约 90%），并具有令人满意的均匀性。交联过程的动力学分析显示log S和log t之间存在线性关系（S是溶胶分数，t是照射时间）。观察到诱导期，其长度随着4-CBP浓度的增加和光强度的增加而缩短。还发现了长照射时间下凝胶含量的上限，其水平取决于4-CBP的浓度。交联率在较低强度下与二级光强度成正比，在较高光强度时变为一级。提出了一种基于通过TAC的烯丙基和烷基型自由基进行链自由基重组的机制。
High density polyethylene has been photocrosslinked in the melt by using 4-chlorobenzophenone (4-CBP) as photoinitiator and triallylcyanurate (TAC) as crosslinking agent. Various factors affecting the crosslinking process (photoinitiator used and its concentration, irradiation temperature and time, atmosphere, UV light source, light intensity) were examined. By optimizing the irradiation conditions, it was found that samples up to 2 mm thick could readily be crosslinked to high gel content (≈ 90%) with satisfactory homogeneity within very short irradiation times (≈ 15 s). The kinetic analysis of the crosslinking process showed a linear relation between log S and log t (S is the sol fraction t is the irradiation time). An induction period was observed, the length of which decreased with increasing concentration of 4-CBP and increasing light intensity. An upper limit of gel content was also found for long irradiation times at a level depending on the concentration of 4-CBP. The crosslinking rate was proportional to the second order of light intensity at lower intensity and changed to first order at higher light intensity. A mechanism based on the recombination of chain radicals through both allyl and alkyl type radicals of TAC was proposed.