On-line measurement, of polymer orientation using ultrasonic technology

The propagation velocity of an ultrasonic shear wave can be used to detect anisotropic behavior in the mechanical properties of a solid. Thus, an ultr asonic shear transducer imbedded in an injection mold produces a signal tha t is sensitive to polymer orientation. This results in a non-invasive, on-l ine technique for monitoring the orientation of polymer in an injection mol d cavity during part cooling and solidification. The technique is shown to be quite sensitive for semicrystalline polymers, but much less effective fo r amorphous polymers. Sensor results are compared to mechanical tests.