摘要
Currently adopted cross-linking methods in rubber industry are suffering from variable persistent issues, including the utilization of toxic curing packages, release of volatile organic compounds (VOCs) and difficulties in the recycling of end-of-life materials. It is of great importance to explore a green cross-linking strategy in the area. Herein, we report a new ‘‘green" strategy based on hydrolyzable ester cross-links for cross-linking diene-typed elastomers. As a proof of concept, a commercial carboxylated nitrile rubber (XNBR) is efficiently cross-linked by a bio-based agent, epoxidized soybean oil (ESO), without any toxic additives. ESO exhibits an excellent plasticization effect and excellent scorch safety for XNBR. The crosslinking density and mechanical properties of the ESO-cured XNBR can be manipulated in a wide range by changing simply varying the content of ESO. In addition, zinc oxide (Zn O) performs as a catalyst to accelerate the epoxide opening reaction and improve the cross-linking efficiency, serving as reinforcement points to enhance the overall mechanical properties of the ESO-cured XNBR. Furthermore, the end-oflife elastomer materials demonstrate a closed-loop recovery by selectively cleaving the ester bonds, resulting in very high recovery of the mechanical performance of the recycled composites. This strategy provides an unprecedented green avenue to cross-link diene elastomers and a cost-effective approach to further recycle the obtained cross-linked elastomers at high efficiency.
本文提出了一种基于可水解酯基的橡胶材料绿色交联策略.选择商品化的羧化丁腈橡胶(XNBR)中的羧基作为交联点,生物基环氧大豆油(ESO)替代硫磺作为交联剂,基于羧基与环氧基团之间的反应,本文构建了一个含酯基的交联网络结构.在交联反应发生前,生物基的ESO还可以起到增塑剂的作用,有着"一剂多用"的效果.此外,氧化锌(Zn O)可作为交联反应的催化剂,提高交联效率;同时,锌离子与羧基形成的离子对或离子簇可作为增强点,从而提高材料的力学性能.这种交联方法不使用任何有毒的化学物质,并且在交联反应过程不会产生挥发性有机物.通过改变ESO或Zn O的用量,可以实现对交联橡胶的交联速率、交联密度和力学性能等的调节.最后,通过化学回收的方法,可以将交联结构中的酯基选择性地断开,得到一种高效的橡胶回收方法.在酸的催化下,橡胶交联结构中的酯基被水解成羟基和羧基,重新得到线性的XNBR.利用该方法, XNBR可以被多次循环使用.
基金
This work was supported by the National Natural Science Foundation of China(NSFC,51790501 and 51825303),the Basic Science Center Program of NSFC(51988102)
the National Key Research and Development Program of China(2017YFB0306900 and 2017YFB0306904)
the Beijing Advanced Innovation Center for Soft Matter Science and Engineering
作者简介
Ganggang Zhang is a Ph.D.candidate under the supervision of Prof.Liqun Zhang at Beijing University of Chemical Technology.His main research interests focus on the design and preparation of functionalized elastomer and green cross-linked elastomer;Corresponding authors:Xinxin Zhou received his B.S.degree from Beijing University of Chemical Technology in 2011 and Ph.D.degree under the supervision of Prof.Guo-Hua Hu and Prof.Liqun Zhang at the University of Lorraine in 2018.He joined the Prof.Liqun Zhang’s group at Beijing University of Chemical Technology as a postdoctoral research fellow in 2018.His current research interests focus on polymer science,nanocomposites as well as green and sustainable chemistry,such as the design and preparation of bio-based elastomers,bio-based elastomeric nanocomposites,and green cross-linked elastomers,E-mail addresses:xinxinzhou@mail.buct.edu.cn;Corresponding authors:Baochun Guo is a Professor in the Department of Polymer Materials and Engineering at South University of Technology(SCUT).After receiving a B.S.degree from Northwestern Polytechnical University in 1996,he completed his Ph.D.degree in Materials Science at SCUT in 2001.Then,he joined the Department of Polymer Materials and Engineering,SCUT as a Lecturer and became Full Professor at SCUT in 2009.His current research involves hierarchical design of rubbers and rubber composites,development and applications of high-performance and functional elastomers,psbcguo@scut.edu.cn;Corresponding authors:Liqun Zhang is a Professor of Beijing University of Chemical Technology.His research interests focus on rubber science and technology,polymer nanocomposites,bio-based polymeric materials and so on,zhanglq@mail.buct.edu.cn。
