Measurement of Ultrasonic Bulk-Wave Propagation in High Polymers

The velocity and attenuation of bulk waves (longitudinal waves of dilatation) in solid samples of high polymers are measured by an acoustic pulse technique in the frequency range 10 to 30 mc. An ultrasonic pulse of about 2 microseconds' duration is transmitted by a crystal into the liquid contained in a tank about 5 cm long, and returns as an echo to the crystal transducer. The velocity of bulk waves in the polymeric material is found from the change in echo arrival time which occurs when a flat sample is introduced into the sound path, and the attenuation is found from the reduction of echo intensity. Measurements for several rubbers and plastics are reported over various portions of the temperature range −60°C to 100°C. The attenuation generally shows at least one maximum with respect to temperature in this range. Maximum attenuation values for various rubbers at 10 mc range from 200 to 400 db/cm.