Flow-Induced Crystallization of PEEK: Isothermal Crystallization Kinetics and Lifetime of Flow-Induced Precursors during Isothermal Annealing

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• 作者：Behzad Nazari ; Alicyn M. Rhoades ; Richard P. Schaake ; Ralph H. Colby
• 刊名：ACS Macro Letters
• 出版年：2016
• 出版时间：July 19, 2016
• 年：2016
• 卷：5
• 期：7
• 页码：849-853
• 全文大小：353K
• 年卷期：0
• ISSN：2161-1653

文摘

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 (T_m), 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 T_m. The persistence of shear-induced structures slightly above T_m, 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.