Is transparency of organic compound crystal depends only on whether polymeric chain entanglement (disorderly arrangement) is on the order of wavelength of light or not? and whether the molecular crystal is monocrystalline or polycrystalline?
Amorphous polymers (e.g. PS) are transparent, semi-crystalline polymers (e.g. PP) are turbid. Transmittance of semi-crystalline polymers can (to some extend) be increased by nucleating agents, decreasing the size of the crystalline spherulites.
The principle is light scattering in other words change in refractive index. It indicates that disorder and crystallinity can play a crucial role.
Dear all, both degree of crystallization and size and perfection of crystallites are respensible for opaqueness. In addition to the control of cristals growth by nucleating agents, quenching (abrupt and rapid cooling down) is another solution to reduce cristal size and enhancing transparency. My Regards
Hi;
Crystalline polymers are usually opaque because of light scattering on the numerous boundaries between the crystalline and amorphous regions. The density of such boundaries is lower and consequentially, the transparency is higher - either for low (amorphous polymer) or high (crystalline) degree of crystallinity.
With my best regards
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