Plastic powder grain structure determn. - by heating suspension in fluid causing swelling and measuring ultrasonic attenuation

摘要

The grain structure of plastic powder is investigated by suspending it in a fluid which can cause it to swell, pref. at normal pressure below the temp. where swelling starts. After stirring the suspension is heated at a constant rate of rise of the temp. to produce a significant swelling. During the heating period the suspension or a part of it is exposed to the sonic vibrations of an ultrasonic generator with a frequency between 0.02 and 20 MHz. The attenuation of the sound waves is measured continuously and represents a direct measure for the grain structure of the plastic powder.