Nazari Behzad, Rhoades Alicyn M, Schaake Richard P, Colby Ralph H
Department of Materials Science and Engineering, Penn State University, University Park, Pennsylvania 16802, United States.
School of Engineering, Penn State Behrend, Erie, Pennsylvania 16563, United States.
ACS Macro Lett. 2016 Jul 19;5(7):849-853. doi: 10.1021/acsmacrolett.6b00326. Epub 2016 Jun 30.
The role of an interval of shear flow in promoting the flow-induced crystallization (FIC) for poly(ether ether ketone) PEEK was investigated by melt rheology and calorimetry. At 350 °C, just above the melting temperature of PEEK (), a critical shear rate to initiate the formation of flow-induced precursors was found to coincide with the shear rate at which the Cox-Merz rule abruptly begins to fail. In cooling the sheared samples to 320 °C, FIC can be up to 25× faster than quiescent crystallization. Using rheology and differential scanning calorimetry, the stability of FIC-induced nuclei was investigated by annealing for various times at different temperatures above . The persistence of shear-induced structures slightly above , along with complete and rapid erasure of FIC-induced nuclei above the equilibrium melting temperature, suggests that FIC leads to thicker lamellae compared with the quiescently crystallized samples.
通过熔体流变学和量热法研究了剪切流动间隔在促进聚醚醚酮（PEEK）的流动诱导结晶（FIC）中的作用。在350℃，刚好高于PEEK的熔点（）时，发现引发流动诱导前驱体形成的临界剪切速率与Cox-Merz规则突然失效时的剪切速率一致。在将剪切后的样品冷却至320℃时，FIC比静态结晶快25倍。使用流变学和差示扫描量热法，通过在高于的不同温度下进行不同时间的退火来研究FIC诱导的核的稳定性。略高于时剪切诱导结构的持续性，以及在平衡熔点以上FIC诱导的核的完全快速消除，表明与静态结晶的样品相比，FIC导致更厚的片晶。
