- Spherulite (polymer physics)
In
polymer physics , spherulites arespherical semi-crystalline regions inside non-branchedlinear polymer s.When a liquid linear polymer (such as
polyethylene ) is cooled down slowly, the polymer strings take on a certain "orderly configuration": they align themselves in plates oforthorhombic unit cell s called "crystalline lamellae". These highly ordered plates are interrupted byamorphous regions, so that even a completely spherulized polymer is still far from being fully crystalline.Due to the high degree of order and crystallinity contained within the spherulite structure they exhibit
birefringence . By placing the polymer spherulite between crossed polarisers different colours can be observed. See image "A PEO spherulite..."The process of spherulization starts on a nucleation site and continues to extend radially outwards until a neighbouring spherulite is reached. This explaines the spherical shape of the spherulite.
Spherulites, when formed, impact some properties of the polymer material: crystallinity,
density (crystalline lamellae are denser than surrounding amorphous material),tensile strength and modulus of elasticity all increase during spherulization.Sources
* cite book
coauthors = C.J. McMahon. Jr, C.D. Graham. Jr
title = Introduction to engineering Materials: The bicycle and the walkman
publisher = Enfield Publishing
date = 1992
location =Philadelphia
pages = pp 277 - 283
isbn = 0-9646598-0-8
* http://www.pslc.ws/mactest/crystal.htm
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