As a response to the need of on-line monitoring for mixing status of polymer in screw extrusion, the ultrasonic wave propagation character during the PEEK buffer rod was studied. The cause of the trailing echoes when the ultrasonic wave was propagating in the PEEK buffer rod was analyzed, and the expressions for locating the position of trailing echoes was given. The influence of the buffer rod shape and cooling device on ultrasonic pulse echo was studied. The experimental results of different ratio between melted PP and CaCO3 showed that the attenuation of the ultrasonic wave propagation during the polymer could characterize the mixing status of polymer.The PEEK buffer rod could be used to monitor mixing status of polymer with melted temperature being lower than 160℃ during screw extrusion.%针对螺杆挤出机中聚合物挤出过程的混合状态的在线监测要求,通过研究超声波在PEEK缓冲杆中的传播特性,分析了超声波在缓冲杆中传播时尾随信号产生的原因,推导了尾随回波出现的位置公式,结合试验,分析了缓冲形状及水冷装置对脉冲回波的影响.不同比例物质聚丙烯(PP)和CaCO3的在线检测试验结果表明,PEEK作为缓冲杆用于检测聚合物混合状态时,超声波的衰减与混合物的混合比例之间存在对应关系,因此可以通过脉冲回波幅值表征聚合物的混合比例.PEEK缓冲杆能用于熔融温度<160℃的聚合物挤出过程中混合状态的在线监测.
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