Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Micrograph Library Full Record for Micrograph 600

Full Record for Micrograph 600

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Micrograph no
600
Brief description
Spherulite in poly-3-hydroxy butyrate (PHB)
Keywords
alignment, crystal Link to MATTER Glossary entry for crystal, polyhydroxybutyrate (PHB), polymer Link to MATTER Glossary entry for polymer, spherulite Link to MATTER Glossary entry for spherulite
Categories
Polymer
System
Polyhydroxybutyrate (PHB)
Composition
Not specified
Standard codes
Reaction
N/A
Processing
4 minutes @ 210ºC, 5 minutes @ 160ºC, followed by quench to room temperature
Applications
Sample preparation
Thin specimen on glass slide with cover slip
Technique
Cross-polarised light microscopy
Length bar
1 μm
Further information
Polymer melts often crystallise from heterogeneous nuclei to form ribbon-like lamellae, which have a folded chain molecular structure. They commonly radiate outwards from the nucleation point, to form spherical features called spherulites - which are often quite large. The characteristic Maltese cross pattern, seen when viewed between crossed polars, results from isoclinic fringes formed when one of the principal vibration directions is approximately parallel to the polariser. In some cases (including the Poly-3-hydroxy butyrate (PHB) viewed here), the lamella twist as they grow outwards, in phase with their neighbours. This gives rise to the observed ring pattern. When viewed with a full wave plate, alternate (fast and slow) rings are coloured blue and yellow.
Contributor
Prof T W Clyne
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
03/10/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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