溶融ポリマの超音波音速と減衰の温度依存性の定量評価

抄録

Temperature dependence of ultrasonic properties such as velocity and attenuation has been evaluated quantitatively in the liquid and solid phases. A polygonal buffer rod that provides appropriate ultrasonic pulse-echo measurements with a high signal to noise ratio is employed. Polyimide is chosen as the rod material for measuring low-density polyethylene (LDPE) because such plastic material provides better acoustic impedance matching with LDPE. Ultrasonic pulse echo measurement with the buffer rod is performed for LDPE at temperatures up to 200 oC. Ultrasonic echoes reflected at the bottom of the LDPE are clearly observed even without any couplant between the rod end and LDPE. Temperature dependences of the ultrasonic velocity and attenuation of the LDPE are then obtained. Both the velocity and attenuation show a bending point at the solidification point of the LDPE.