Abstract
Experiments on the internal heating effect of ultrasonic waves in high polymers were performed, giving the following main results. (1) For the case of radiation of the ultrasonic waves into the polyvinylchloride plates, the temperature rise by the absorption of ultrasonic waves are in a comparatively good agreement with the calculation; the value in the depth of 3 mm attaining to 70-80 ℃, even when a small portable ultrasonic apparatus of frequency 960 kc and intensity of 2 watt/cm^2 is used. (2) When the ultrasonic waves are radiated into two high polymer plates glued together by a proper adhesive, it is possible to make the temperature rise in the rear plate rather higher than in the front plate, provided the former has a very high absorption coefficient for ultrasonic waves. Similarly the high polymer plates can be efficiently heated even through thick metal plates, owing to the negligible absorption in metals and the selective ultrasonic absorption in high polymer. (3) The time required for adhesion (by Araldite 121) of two high polymer plates is extremely shortened by ultrasonic irradiation, because of the promotion of the polymerization of adhesive by the internal temperature rise. These experiments suggest that it is worth while to investigate the ultrasonic waves from the viewpoint of internal heating, even though these may be many limitations and difficulties in adaptability, as compared with the widely used radio-heating apparatus.
