Transparency of Poylmers (1 Viewer)

[HSC2014]

Why do amorphous polymers tend to be transparent whilst crystalline polymers tend to be translucent/opaque? It seems counter intuitive.

 

[HeroicPandas]

Why do amorphous polymers tend to be transparent whilst crystalline polymers tend to be translucent/opaque? It seems counter intuitive.

An amorphous polymer (eg. LDPE), has chain branching and therefore cannot pack closely together in an orderly fashion and so the great amounts of gaps present (between each polymer molecule) will cause it to be transparent

A crystalline polymer (eg. HDPE), has unbrached chains (no chain branching), thus can pack closely to form a crystalline structure and since there are less gaps, it appears to be opaque

I think...

 

[someth1ng]

HeroicPandas is correct in terms of HSC, as far as I know.

The actual reason is that light is scattered more in crystalline polymers than in amorphous polymers, causing crystalline solids to appear opaque while amorphous polymers appear transparent.

It's a bit a like clean water compared with dirty water. Clean water doesn't scatter light that much but if you add dirt into it, light gets scattered erratically by suspended particles in it, resulting in opacity.