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Diffusion of liquids into semicrystalline polyethylene
1Department of Chemical Engineering, University of Cambridge, UK.
Magnetic Resonance Imaging
|November 6, 1998
Summary
Pulsed field gradient nuclear magnetic resonance (PFG NMR) reveals how crystalline structures in polyethylene (PE) hinder alkane diffusion. The crystals impede penetrant movement and affect polymer chain mobility in the amorphous regions.
Area of Science:
- Polymer Science
- Materials Science
- Physical Chemistry
Background:
- Semicrystalline polymers like polyethylene (PE) exhibit complex diffusion behaviors.
- Understanding penetrant diffusion in polymers is crucial for material design and application.
Purpose of the Study:
- To investigate the diffusion dynamics of liquid alkanes within semicrystalline polyethylene.
- To elucidate the role of the crystalline phase in controlling diffusion.
Main Methods:
- Pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy.
- Microimaging techniques.
- Diffusion studies using liquid alkane penetrants in various PE samples.
Main Results:
- The crystalline phase significantly impedes the diffusion of liquid alkanes into polyethylene.
- Impenetrable crystals create geometric barriers for penetrant migration.
- Crystallinity influences polymer chain mobility within the amorphous regions, further affecting diffusion.
Conclusions:
- The crystalline structure is a primary determinant of alkane diffusion rates in semicrystalline PE.
- Both physical obstruction and altered chain dynamics contribute to diffusion control.
- PFG NMR is effective in characterizing diffusion mechanisms in polymer systems.