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In polymers under strain, white lines start to appear first before fracture..what are they? And why they occur?

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the white zones are where the polymer molecule chains have slid past one another slightly and have begun getting their long axes slightly aligned with one another. The chains also are getting snagged and tangled up on one another. Polymer scientists say that the molecules are beginning to exhibit "crystallinity" which means long-range order in this state. These effects cause a clear plastic to become slightly milky in appearance because of optical scattering off of the oriented microdomains.

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  • $\begingroup$ The optical phenomenon should be scattering from the oriented/crystalline microdomains. $\endgroup$
    – Alchimista
    Sep 23, 2019 at 9:33
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    $\begingroup$ There is also crazing, the development of small voids, which also makes for a cloudy or milky appearance. $\endgroup$
    – Jon Custer
    Sep 23, 2019 at 17:00

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