聚丙烯和聚乙烯熔融过程的超声波扫描热学分析

Analysis of the Melting Behavior of Polypropylene and Polyethylene by Ultrasonic Scanning Calorimetry Measurements

用建立的超声波和PVT同步检测装置检测了聚丙烯和聚乙烯的熔融行为。改变温度,高密度聚乙烯中超声波曲线与动态扫描量热学(DSC)曲线有一定相似性,可反映熔融过程。不同压力下超声曲线相似;随压力升高,熔融起始温度、峰值温度和结束温度都向高温几乎呈线性偏移。粒料和密实本体料的密度随温度变化规律不同,基于机械波特性的超声振幅和衰减曲线能体现其变化特点。可见,超声波扫描热学(USC)可研究压力和时间对聚合物熔融的影响,接近工程条件,可用于在线检测。

Melting behavior of polypropylene and polyethylene was investigated by an instrument for simultaneous characterization of ultrasonic wave and pressure-volume-temperature. Ultrasonic curves were comparable to dynamic scanning calorimetry （DSC）curves for high density polyethylene at different temperatures in reflecting the melting process. Ultrasonic curves were similar at different pressures. Onset, peak and end temperatures ahnost linearly shifted to higher temperature with the increase of the pressure. The density of pellets and bulk blocks varied in different ways with temperatures, which were sufficiently suggested by ultrasonic amplitude curve and velocity curve due to its mechanical characteristics. The quantitative comparison of ultrasonic curves with DSC curves confirmed the feasibility of ultrasonic scanning ealorimetry（USC）in analyzing melting at different pressures and meeting the requirements of on-line testing.