Crazes

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As crazes ( Engl. : Hairline cracks ) are microscopic crack networks as a precursor to a stress cracking in plastics called.

In plastic components that are under mechanical tension , the polymer chains can align themselves regularly. If the tension becomes too great, microcrack-like structures that are connected by fibrils can form at the aligned points . Macroscopically, they appear as fracture-like patterns on the surface. When exposed to tension and media, they can grow into larger cracks and ultimately lead to component breakage.

Some amorphous plastics are affected by this effect. For example, it can be observed very well when bending transparent polystyrene (plastic ruler ) that has aged due to the incidence of light or has been in contact with a medium that can cause stress cracks, such as ethanol .

literature

  • Wolfgang Grellmann, Sabine Seidler: Deformation and fracture behavior of plastics. Springer Verlag, Berlin / Heidelberg 1998, ISBN 978-3-642-63718-6 .

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