Novel Approaches to In-Situ ATR-FTIR Spectroscopy and Spectroscopic Imaging for Real-Time Simultaneous Monitoring Curing Reaction and Diffusion of the Curing Agent at Rubber Nanocomposite Surface

Shun Muroga; Yu Takahashi; Yuta Hikima; Seisuke Ata; Sergei G Kazarian; Masahiro Ohshima; Toshiya Okazaki; Kenji Hata

doi:10.3390/polym13172879

Novel Approaches to In-Situ ATR-FTIR Spectroscopy and Spectroscopic Imaging for Real-Time Simultaneous Monitoring Curing Reaction and Diffusion of the Curing Agent at Rubber Nanocomposite Surface

Polymers (Basel). 2021 Aug 27;13(17):2879. doi: 10.3390/polym13172879.

Authors

Shun Muroga¹, Yu Takahashi², Yuta Hikima², Seisuke Ata¹, Sergei G Kazarian³, Masahiro Ohshima², Toshiya Okazaki¹, Kenji Hata¹

Affiliations

¹ CNT-Application Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 5, 1-1-1, Higashi, Tsukuba 305-8565, Japan.
² Department of Chemical Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
³ Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.

Abstract

Here, we propose a novel attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy method for simultaneously monitoring the curing reaction and the diffusion behavior of curing agents at the surface of rubber in real-time. The proposed scheme was demonstrated by fluorine rubber (FKM) and FKM/carbon nanotube (CNT) nanocomposites with a target curing agent of triallyl-isocyanurate (TAIC). The broadening and the evolution of the C=O stretching of TAIC were quantitatively analyzed to characterize the reaction and the diffusion. Changes in the width of the C=O stretching indicated the reaction rate at the surface was even faster than that of the bulk as measured by a curemeter. The diffusion coefficient of the curing agent in the course of heating was newly calculated by the initial increase in the absorbance and our model based on Fickian diffusion. The diffusion coefficients of TAIC during curing were evaluated, and its temperature and filler dependency were identified. Cross-sectional ATR-FTIR imaging and in situ ATR-FTIR imaging measurements supported the hypothesis of the unidirectional diffusion of the curing agent towards the heated surface. It was shown that our method of in situ ATR-FTIR can monitor the degrees of cure and the diffusion coefficients of curing agents simultaneously, which cannot be achieved by conventional methods, e.g., rheological measurements.

Keywords: Fourier transform infrared spectroscopic imaging; carbon nanotube; curing reaction; diffusion; fluorine rubber; in situ attenuated total reflection infrared spectroscopy; polymer nanocomposite; triallyl isocyanurate.