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

DoITPoMS Micrograph Library Full Record for Micrograph 591

Full Record for Micrograph 591

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Micrograph no
Brief description
Crazing near a fracture surface in polycarbonate
craze Link to MATTER Glossary entry for craze, fibril Link to MATTER Glossary entry for fibril, fracture Link to MATTER Glossary entry for fracture, polycarbonate (PC), polymer Link to MATTER Glossary entry for polymer
Fracture, Polymer
Polycarbonate (PC)
Not specified
Standard codes
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
Scanning electron microscopy (SEM)
Length bar
80 μm
Further information
The fracture surface shows fibrils of oriented polymer which are the remnants of crazes. 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. The surface ridging, parallel to the principal stress, is a consequence of strain-induced crystallisation during the cold drawing of the polycarbonate.
J A Curran
Department of Materials Science and Metallurgy, University of Cambridge
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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