HIGH-SPEED MEASUREMENT OF SURFACE TENSIONAND VISCOSITY OF BINARY POLYMER SOLUTIONSBY THE SURFACE LASER-LIGHT SCATTERING METHOD

摘要

Surface laser-light scattering method (SLLS), which can measure the surface tension and the viscosityrnsimultaneously, has been developed. These properties can be obtained by the laser heterodyne detection ofrnlight scattered from the capillary waves (called ripplon) excited by thermal fluctuations on a liquid surface.rnDistinctive features of this measurement system are as follows; (1) high-speed (maximum 1 measurement/s)rnsurface phenomena can be observed, (2) 2-dimensional surface tension and viscosity can be observed byrnscanning SLLS system horizontal to the sample, and (3) non-contact and in situ measurement can be carriedrnout. Since SLLS method is possible to detect temporal and local behavior of the surface properties, thisrnadvantage can be applied to manufacturing in-line process where it is difficult to insert an actuator or a sensor inrna sample. In the present study, we have validated in situ and high-speed measurement using SLLS. As thernfirst step, we have measured the time-dependent surface tension of water gradually contaminated by addingrnsurfactant. Next the surface tension of 50 mass% methanol aqueous solution has been measured. Thernelevation of surface tension with time has been observed. High-speed surface phenomena generated by therndifferent evaporation rates have been detected. Moreover we have measured CAB (cellulose acetate butyrate)rnsolutions in MEK (metyl ethyl ketone) under different conditions of CAB mass%. As the CAB concentrationrnwas increased, measured surface tension became lower than that of bulk values measured by the static methodrn(surface tension: plate method, viscosity: oscillation viscometer.) This difference may be caused by thernmonolayer film formed on thin surface of the sample. From a series of present experiment, it is indicated thatrnSLLS system can observe the high-speed surface phenomena which cannot be detected by the conventionalrntechniques, and that it can be applied to the actual manufacturing processes.