To obtain a sufficiently accurate fiber particle*1 content in titanate, which is one of a quite important brake pad additives, with a industrially practical method, we are recommending what is called "Dynamic Image Analysis" (DIA) as a measurement method from viewpoints of accuracy and simplicity. In the last EuroBrake conference in 2019, we compared this method to SEM observations and demonstrated that DIA is quite effective to obtain sufficiently accurate content of the fibers in titanate products with industrially affordable burden for examination. For example, around 70,000 particles can be analyzed in 10 min and a fiber content value can be obtained simultaneously. Analytical results for some fine particles smaller than 20µm well agreed with the results by SEM observation.

In the present study, some issues and attentions in the measurement of fiber particle contents by DIA are discussed.

PITA-3 (Seishin Enterprise Co., Ltd.) was used as a DIA method in the study. This is a kind of an optical method, in which water suspended particles flow in the narrow flow cell and a photograph of each particle is taken by a CCD camera, and then it is numerically analyzed. One of the issues of this method is high magnification observation which is barred by resolution limit of the optical system. However, by using high magnification objective lens and a high resolution CCD camera as well as the optimum contrast adjustment, particles of 0.45µm in width (length of short axis of the particle) or larger can be investigated. In addition, the adjustment of flow cell and some treatment for the numerically obtained data for each particle enable us to access more accurate fiber content values. Here it should be noted that very fine particles smaller than 0.45µm do not affect the fiber content value because it is designated by mass % and every particle is too small and light to affect the total mass % of fiber particles. In addition, it was confirmed by SEM observations that most of those fine particles in the titanate observed in the study had an aspect ratio less than three. It indicates that by using SEM observation supplementally, DIA method can be fully used as a simple and accurate measurement method for fiber particle content in titanate products.

Use of this method is believed to give a lot of advantages to all industry sectors involved in the brake-pad field not only for suppliers of the titanate but also manufactures and users.

*1 length of major axis ; 5 µm or over, length of minor axis ; 3 µm or under, aspect ratio ; 3 or over

Dr. Eng. Hideki Fujii, General Manager, Toho Titanium Co., Ltd.; Mr. Daisuke Taki, Toho Titanium Co., Ltd.; Mr. Kohei Yamaguchi, Toho Material Co., Ltd.