紫外引发的交联反应机理和交联聚乙烯的电击穿性能。,Polymers

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紫外引发的交联反应机理和交联聚乙烯的电击穿性能。
Polymers ( IF 4.7 ) Pub Date : 2020-02-12 , DOI: 10.3390/polym12020420
Yu-Wei Fu ₁ , Wei-Feng Sun ₁ , Xuan Wang ₁

Affiliation

通过第一性原理计算，从理论上研究了聚乙烯的紫外（UV）照射交联反应以及光引发剂和反应产物的电子性质。交联聚乙烯（XLPE）材料是在实验中采用不同光子引发系统的紫外线引发交联技术制备的。通过红外光谱和紫外引发XLPE的交流电击穿强度测试，结合电子结构计算探讨反应产物对击穿特性的影响。理论计算表明，与聚乙烯相容的4-羟基二苯甲酮月桂酸酯在紫外光子激发下能有效引发聚乙烯分子的交联反应，并产生羰基自由基的反应副产物；作为大分子辅助交联剂，二油基-2,2',4,4'-四烯丙基异氰脲酸酯的单体或均聚物可以与多个聚乙烯分子形成化学连接，在光子引发反应过程中充当交联节点。反应副产物的羰基、羟基或酯基能够捕获热电子，阻止聚乙烯分子碰撞电离，从而增加击穿电场。高分子辅助交联剂和高分子光子引发剂及其反应副产物可以将其捕获的高能电子的能量转化为热能，从而起到稳压作用。红外光谱分子表征表明，随着交联反应的进行，高分子光子引发剂中的羰基和高分子辅助交联剂中的烯丙基的特征吸收峰强度逐渐减弱，这与理论计算的结论一致。与光子引发交联过程中普遍使用的小分子光子引发体系相比，利用高分子光子引发体系制备的XLPE具有更高的介电击穿电场，与电子亲和力和电离势的计算结果吻合较好。实验和第一性原理计算的一致结果阐明了紫外引发交联技术的基本机制，并为开发高压XLPE绝缘材料提出了提高绝缘强度的前瞻性方案。

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UV-Initiated Crosslinking Reaction Mechanism and Electrical Breakdown Performance of Crosslinked Polyethylene.

The ultraviolet (UV) irradiation crosslinking reactions of polyethylene and the electronic properties of photo-initiators and reaction products are theoretically investigated by the first-principles calculations. The crosslinked polyethylene (XLPE) materials are prepared in experiments that employ the UV-initiated crosslinking technique with different photon-initiation systems. Infrared spectrum and the alternating current dielectric breakdown strength of UV-initiated XLPE are tested to explore the effect of reaction products on the breakdown characteristics in combination with the electron structure calculations. The theoretical calculations indicate that the 4-hydroxybenzophenone laurate, which is compatible with polyethylene, can effectively initiate crosslinking reactions of polyethylene molecules under UV photon excitation and will produce reaction by-products from carbonyl radicals; as a macromolecular auxiliary crosslinker, the monomer or homopolymer of dioleyl-2,2',4,4'-tetraallyl isocyanurate can form chemical connections with multiple polyethylene molecules acting as a crosslinking node in a photon-initiated reaction process. The carbonyl, hydroxyl, or ester groups of reaction by-products are capable of capturing hot electrons to prevent polyethylene molecules from impact ionization, and thus will increase the breakdown electric field. The macromolecular auxiliary crosslinker and the macromolecular photon initiator as well as its reaction by-product can convert the energy of their captured high-energy electrons into heat, which can act as a voltage stabilizer. The molecule characterization of infrared spectra demonstrates that the characteristic absorption peaks of the carbonyl in the macromolecular photon initiator and the allyl in the macromolecular auxiliary crosslinking agent are gradually decreasing in intensity as the crosslinking reaction proceeds, which is consistent with the conclusion from theoretical calculations. Compared with the small molecular photon-initiation system generally used in the photon-initiated crosslinking process, the higher dielectric breakdown field of XLPE being prepared by utilizing a macromolecular photon-initiation system is in good agreement with the calculation results of electronic affinity and ionization potential. The consistent results of the experiments and first-principles calculations elucidate the fundamental mechanism of the UV-initiation crosslinking technique and suggest a prospective routine to improve the insulation strength for developing high-voltage XLPE insulating materials.

更新日期：2020-02-12

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