Quantitative ultrasonic characterization of layered polymer structures

Tubular layered polymer structures are used e.g. in the medical industry for controlling chemical release. An ultrasonic 50 MHz pulse-echo immersion method was employed to characterize layered polymer structures for quality control purposes. The method can non-invasively determine layer thickness, interface delaminations, and sound velocity in the samples. Assuming constant layer density allows determining the sound velocity from the first surface reflection. The layer thickness is then calculated from the time of flight inside the layer. The determined sound velocity value is linked to the cross-linkage degree of the polymer. Delaminated areas between the layers as well as embedded defects are detected in the ultrasonic images. The method could be used to study the quality of polymer structures in laboratory conditions and holds potential for on-line application.