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Spherulite in poly-3-hydroxy butyrate (PHB) | by CORE-Materials
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Spherulite in poly-3-hydroxy butyrate (PHB)

DoITPoMS, University of Cambridge

 

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.

 

System

Polyhydroxybutyrate (PHB)

 

Composition

Not specified

 

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

 

Contributor

Prof T W Clyne

 

Organisation

Department of Materials Science and Metallurgy, University of Cambridge

 

View micrograph in DoITPoMS website

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Taken on October 3, 2002