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

DoITPoMS Micrograph Library Full Record for Micrograph 592

Full Record for Micrograph 592

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Micrograph no
592
Brief description
The tip of a craze in polycarbonate
Keywords
craze Link to MATTER Glossary entry for craze, fibril Link to MATTER Glossary entry for fibril, polycarbonate (PC), polymer Link to MATTER Glossary entry for polymer
Categories
Fracture, Polymer
System
Polycarbonate (PC)
Composition
Not specified
Standard codes
Reaction
Processing
Applications
Polycarbonate is a clear and relatively tough plastic used to make shatterproof windows, lenses and even helmets. It is also used to make compact discs.
Sample preparation
To induce crazing in polycarbonate, acetone is used. This results in the otherwise tough material becoming very brittle
Technique
Scanning electron microscopy (SEM)
Length bar
4 μm
Further information
Fibrils of oriented polymer are visible in the tip of the remnant of a craze near a fracture surface in a fractured specimen of polycarbonate. Crazes are both a precursor to cracking and a toughening mechanism in stressed polymers. They only form when a certain critical tensile stress has been attained and form perpendicular to the largest tensile principal stress. They are very fine crack-like projections from the fracture surface but are bridged by even finer material, giving approximately 50% voids. It is these fibrils which interfere with light in an otherwise transparent polymer to make the crazing visible as a whitening of the strained material.
Contributor
J A Curran
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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