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08:01
A Microfluidic Approach for the Study of Ice and Clathrate Hydrate Crystallization
Published on: August 18, 2022
Crystallization and dissolution of flow-induced precursors.
Luigi Balzano1, Nileshkumar Kukalyekar, Sanjay Rastogi
1Department of Chemical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.
Physical Review Letters
|March 21, 2008
Summary
This study shows how to create only extended-chain (shish) crystals in polyethylene using specific processing conditions. These shish crystals form from metastable precursors that grow and crystallize above the melting temperature.
Area of Science:
- Polymer Science
- Materials Science
- Crystallization
Background:
- Extended-chain (shish) crystals are crucial in high-performance polymers.
- Controlling shish crystal formation is challenging due to complex polymer dynamics.
Purpose of the Study:
- To demonstrate the exclusive production of extended-chain (shish) crystals.
- To investigate the formation mechanism of shish crystals from metastable precursors.
Main Methods:
- Utilizing specially synthesized linear high-density polyethylene with bimodal molecular weight distribution (MWD).
- Applying shear flow (120 s⁻¹ for 1 s) at high temperatures (142°C), near the equilibrium melting point (Tm(0)=141.2°C).
- Employing X-ray scattering to analyze crystal structures and precursor dynamics.
Main Results:
- Production of a suspension containing only extended-chain (shish) crystals.
- Observation of numerous metastable, needle-like precursors with low crystallinity post-shear.
- Correlation of precursor dissolution timescale with the reptation time of longest polymer chains.
- Crystallization of precursors exceeding a critical size into extended-chain shishes.
Conclusions:
- Exclusive formation of shish crystals is achievable under specific high-temperature, high-shear conditions.
- Metastable precursors play a critical role, with their size determining subsequent crystallization.
- The findings provide insights into polymer crystallization mechanisms and control.
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