This report summarizes research supported by I.F.P.R.I. at Stanford University on the use of high speed optical polarimetry measurements to characterize the dynamics and structure of fine particle suspensions. This reporting period is the second year of the funding period. During the first year, the research effort considered application of optical rheometry to several fundamental problems in particulate dynamics. These included (1) the characterization of single particle properties, such as size and shape distributions, and dipole moments, (2) the structure of dense suspensions subject to electric fields, 2 and (3) the structure/property relationships of shear thickening suspensions. These projects have each yielded publications and served to introduce the I.F.P.R.I. community to the measurement techniques available in our laboratory.
Our efforts this past year have been directed towards developing these methods in a form that will facilitate their use within industrial applications. This objective has involved two activities: (1) the development of oblique transmission as a means of analyzing optically dense materials, and (2) collaboration with scientists in several member companies to investigate specific applications.The principal impediment of the use of optical methods is the opacity of most indus- trial suspensions. Although some systems will never be accessible to optical methods, many mate- rials can be studied if their optical density is sufficiently lowered. This normally requires thin specimens, which makes it difficult to fully characterize their dynamics and structure in different planes of the applied flow field. The development of the method of oblique transmission is aimed at circumventing this problem. Ultimately, this method may make it possible to apply this tech- nique “on-line” or “in-line” to provide a non-intrusive prove of structure in industrial processes. During the past year, the principal investigator has collaborated with three member companies to identify areas of application of the techniques, and particularly for potential on-line applications. The companies included: Hosokawa Micron Corp. (contact: Mr. Toyokazu Yokoyama), 3M Com- pany (contact: Dr, Caroline Ylitalo), and Procter and Gamble Company (contact: Dr. David Githuku), In each case, a variety of samples were analyzed using the optical rheometric system developed over the past year. In two of these cases, the results were sufficiently promising to encourage the development of similar instrumentation in-house.