Professor in Kyoto Institute of Technology

Director, Center for Rubber Science and Technology in Kyoto Institute of Technology 

Title : New Aspects of Vulcanization and Reinforcement in Rubber Science and Technology

Abstract

The sulfur cross-linking reaction of rubber, i.e., vulcanization is one of the most important reactive processes in polymer technology. An important key to control the network formation by sulfur cross-linking is still sought for the development of the rubber industry. We have studied on the vulcani-zation mechanism and found that the combination and composition of zinc oxide (ZnO) with other rea-gents are crucial to control the structural network inhomogeneity in the N-(1,3-benzothiazol-2-ylsulfanyl)cyclo-hexanamine (CBS) accelerated vulcanization of isoprene rubber (IR) 1 A time-resolved zinc K-edge X-ray absorption fine structure (Zn K-edge XAFS) spectroscopy showed the two-phase network formation.2 The observations are very important for rubber science and technology. However, it was not unclear why the combination of ZnO and StH can be a key for controlling the mesh size of CBS accelerated vulcanizates. On the way to determine the role of the zinc salt of StH in the vulcanization reaction, we found the formation of a specific structural complex generated from ZnO and StH at a high temperature by a combination of time-resolved Zn K-edge XAFS spectroscopy and time-resolved infrared spectroscopy.3,4 The structure is dominantly a bridging bidentate zinc/stearate complex, the molar ratio of the zinc ion to stearate was unexpectedly one. Combination with a density functional calculation for identifying the intermediate predominantly suggests that its most possible structure is (Zn2(μ-O2CC17H35)2)2+(OH−)2•XY as shown in Figure 1. This intermediate has been unknown despite the long history of rubber science and technology. The newly observed zinc/stearate complex may play a role to accelerate the sulfur cross-linking reaction of rubber.
A filler network, on the other hand, is also an im-portant topic in rubber science and technology to reveal a reinforcement effect by filler mixing for rubber materials. However, a selective formation of clear filler network structure has been difficult due to various kinds of filler aggregation by the mechanical mixing. Recently, a combination of in situ silica fill-ing in the natural rubber (NR) latex and solution casting was found to be a good method to produce the model nanocomposites providing a filler network.5,6

Biography

Prof. Dr. Yuko Ikeda received her Bachelor of Engineering from Kyoto Institute of Technology in 1984, and her Master of Engineering degree from Graduate School, Kyoto Institute of Technology in 1986 and Doctor of Engineering from School of Engineering, Kyoto University in 1991 with her thesis entitled “Studies on Blood-Compatible Polyurethanes with Triblock Polyether Soft Segments”. Throughout 1991-1997, she became the visiting researcher in various institutions like Hyogo Prefecture Technology Center, University of Bayreuth, Germany and Texas Christian University of U. S. A. In 2007, she was appointed as associate professor of Kyoto Institute of Technology and promoted to full professorship in 2014. She is also the Director of Center for Rubber Science and Technology in the same institution. Her research interests include fundamental studies on the sulfur cross-linking and reinforcement of rubbers by using new analytical methods as well as characterization of natural rubbers by using synchrotron X-ray analysis. Prof. Dr. Yuko Ikeda has published around 126 original papers, 43 books, 63 reviews, 21 patents and 16 essays so far. She has received quite a few awards from Society of Rubber Industry, Japan including excellent paper awards in 1986 and 1996, 3th Excellent Presentation Award in 2008 and 29th Oenslager Award in 2014 with her research work entitled “Fundamental Study on Cross-linking of Rubber”.