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Micrograph 576 and full record
- Micrograph no
- 576
- Brief description
- Injection-moulded protractor
- Keywords
- alignment, birefringence
, injection moulding , polymer , polystyrene (PS), protractor, sprue, weld - Categories
- Polymer
- System
- Polystyrene (PS)
- Composition
- Not specified
- Standard codes
- Reaction
- Processing
- Polystyrene was injected into a mould from a single point and has flowed round the component to meet at two noticeable 'weld lines'
- Applications
- Polystyrene is hard and inexpensive and its use is very widespread. CD cases and clear plastic cups are common examples. Domestic appliance casings are also typically made from PS
- Sample preparation
- Technique
- Cross-polarised light microscopy
- Length bar
- 30 mm
- Further information
- The colours in the image are the result of birefringence and relate to the residual strain in the polystyrene. The pattern of strain is indicative of the flow of material during the injection process and it highlights the injection point (at 152 degrees on the outer scale), and two 'weld lines' (at 338 and on the central bar) where two distinct flows of material meet. The weld line is a common point of failure because there is limited intermixing of the two fronts during the time allowed.
- Contributor
- J A Curran
- Organisation
- Department of Materials Science and Metallurgy, University of Cambridge
- Date
- 03/10/02
- Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International- Related micrographs
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