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DoITPoMS Micrograph Library Full Record for Micrograph 641
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Full Record for Micrograph 641

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Micrograph no
641
Brief description
Fracture surface in a liquid crystalline polymer
Keywords
alignment, fibre Link to MATTER Glossary entry for fibre, fibrillation Link to MATTER Glossary entry for fibrillation, fracture Link to MATTER Glossary entry for fracture, liquid crystalline polymer (LCP), lyotropic, magnetic, nematic, polymer Link to MATTER Glossary entry for polymer
Categories
Fracture, Polymer
System
Liquid crystalline polymer
Composition
Random copolyester of average molecular weight 14401
Standard codes
Reaction
Processing
No external field has been applied
Applications
The molecules in a LCP mesophase can be steered by external fields; a property used in display technology. Alignment is also exploited in high strength fibres like Kevlar and mouldable Vectra
Sample preparation
Technique
Scanning electron microscopy (SEM)
Length bar
12 μm
Further information
Above their melting point, liquid crystalline polymers exhibit a mesophase within which, although able to flow and are not arranged in a crystal, they exhibit long range orientational order. This molecular alignment can be exploited to make high strength and stiffness fibres such as Kevlar, or even mouldable thermotropics such as Vectra. Molecular alignment can also be controlled by an external applied field; a property exploited in liquid crystal displays. This specimen has not had a magnetic field applied to it and it exhibits only local molecular self-alignment, without any overall orientation alignment. It is to be compared with a similar sample which has been subjected to a magnetic field of 1.1T for one hour and in which there is a high level of fibrillar alignment.
Contributor
Prof A H Windle
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
03/10/02
Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International
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