Stress-whitening scattered light

Finally, it should be noted that stress-whitening arises because these voids, created by cavitation and debonded particles, scatter light. Hence, it is observed that the most intense stress-whitening is present in the recipe that undergoes the greatest extent of particle cavitation and debonding. 

Stress whitening n. Whiteness seen in some plastics and rubbers that are subjected to extreme stretching, thought to be due to the formation of light-scattering Microvoids (microcavitation) within the material. 

Apart from mechanics, crystallinity also influences secondary properties, such as transparency or light scattering, as well as stress whitening, which is an especially unpleasant effect in PP. All of these are also negatively influenced by aging. 

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