Roth Benedikt, Wildner Wolfgang, Drummer Dietmar
Institute of polymer technology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Am Weichselgarten 9, 91058 Erlangen, Germany.
Polymers (Basel). 2020 Feb 22;12(2):488. doi: 10.3390/polym12020488.
This study presents a method for the determination of the dynamic pressure-dependent solidification of polycarbonate (PC) during flow using high pressure capillary rheometer (HPC) measurements. In addition, the pressure-dependent solidification was determined by isothermal pressure-volume-temperature (pvT) measurements under static conditions without shear. Independent of the compression velocity, a linear increase of the solidification pressure with temperature could be determined. Furthermore, the results indicate that the relaxation time at a constant temperature and compression rate can increase to such an extent that the material can no longer follow within the time scale specified by the compression rate. Consequently, the flow through the capillary stops at a specific pressure, with higher compression rates resulting in lower solidification pressures. Consequently, in regard to HPC measurements, it could be shown that the evaluation of the pressure via a pressure hole can lead to measurement errors in the limit range. Since the filling process in injection molding usually takes place under such transient conditions, the results are likely to be relevant for modelling the flow processes of thin-walled and microstructures with high aspect ratios.
本研究提出了一种利用高压毛细管流变仪（HPC）测量来确定聚碳酸酯（PC）在流动过程中动态压力依赖凝固的方法。此外，通过在无剪切的静态条件下进行等温压力-体积-温度（pvT）测量来确定压力依赖凝固。与压缩速度无关，可以确定凝固压力随温度呈线性增加。此外，结果表明，在恒定温度和压缩速率下，松弛时间可能会增加到材料在压缩速率规定的时间尺度内不再能跟随的程度。因此，通过毛细管的流动在特定压力下停止，压缩速率越高，凝固压力越低。因此，关于HPC测量，可以表明通过压力孔评估压力在极限范围内可能导致测量误差。由于注塑成型中的填充过程通常在这种瞬态条件下发生，这些结果可能与高纵横比薄壁和微结构的流动过程建模相关。
