Study On Ultrasonic Transducer For Ultrasonic On-line Testing Of Mixing Status Of Molten Polymer

The polymer's properties, such as impact strength, tensile strength and rigidity, are dramatically improved when some filler is added in. During the extrusion process, the mixing status of polymer and filler in extruder has great impact on the final quality and property of the production. Consequently, to study the on-line testing technique of the molten polymer's mixing status has practical significance on polymer production. According to the characteristic of the extrusion processing, the ultrasonic transducers which are used to test the mixing status of polymer are designed and fabricated in order to realize the on-line testing of the polymer.In this article, the scheme for ultrasonic on-line testing of polymer mixing status is put forward on the basis of the working principle of the extruder and the extruding process of the polymer. Firstly, according to the basic theory of ultrasonic propagating, the ultrasonic propagating principle in the buffer rod is analyzed through experiments. The experiment results show that the ultrasonic echoes propagating in the buffer rod are affected by the shape (e.g. diameter, length) and the properties (e.g. velocity, attenuation, impedance) of the buffer rod. Secondly, based on the ultrasonic propagating principle and the requests of on-line ultrasonic testing of polymer mixing status, a kind of ultrasonic transducer witch is composed of ultrasonic probe, ployetheretherketone(PEEK) and cooling device is designed. Thirdly, the temperature stability of ultrasonic transducer is studied through experiment, and also studies the method for characterizing the mixing status of molten polymer by ultrasonic characteristic parameters. The experiment results indicate that the polymer's characteristic echo has higher signal-to-noise ratio and ultrasonic transducer can test the mixing status of compound with different ratio of polymer and fillers. Finally, the fabricated ultrasonic transducer is used to test the mixing status of molten polymer in the process of on-line experiment. The influence of screw structure of extruder's on characteristic echo of polymer is analyzed. The results show that the fabricated ultrasonic transducer can be used to do on-line testing of mixing status of molten polymer, and the polymer's characteristic echo has higher signal-to-noise ratio. The studies in this article can be the basement for ultrasonic on-line testing of polymer mixing status.