抄録
The change in absorption and velocity of pulsed ultrasonic waves (6.6 Mc/s) in process of gelation has been studied for polyethylene solutions in benzene and xylene as well as aqueous solutions of gelatin and starch. The absorption is found to depend strongly on cooling rate. In the case of polyethylene, the absorption (excess absorption over the absorption by pure solvent) occurs both at rapid and slow rates of cooling, the value being larger in the former case than in the latter. In the cases of gelatin and starch the absorption takes place only at rapid cooling. In all cases the absorption can be attributed to scattering of sound waves by inhomogeneity in gel. The absorption tends to vanish in several ten minutes after gelation, indicating the diminution of inhomogeneity. Only for starch gel, the absorption again increases gradually in several hours, presumably owing to syneresis. No anomaly was found in sound velocity in course of gelation.
