Development of in situ, nondestructive inspection technique of the internal deformation of a black rubber by terahertz polarization spectroscopy

Associate Professor Shinichi Watanabe and Assistant Professor Makoto Okano (Department of Physics, Faculty of Science and Technology, Keio University) succeeded in developing the nondestructive inspection technique of a black rubber with a high-speed and accurate terahertz polarization measurement system. It has been difficult to observe the internal state of the black rubbers including carbon black particles that act as a reinforcing filler by using visible, near-infrared, and mid-infrared light. This innovative achievement was based on the high transmissivity of terahertz waves through the black rubbers, and their polarization information can be used to estimate the internal anisotropy, which is closely linked to the internal deformations. This method is expected as a novel nondestructive testing tool of tires and rubber vibration isolators.