Chemistry Reference
In-Depth Information
POLYMER CRYSTALLINITY
Crystallinity property effects
Polymers <100% crystalline
Regularity of structure needed for high crystallinity
Stretching
Cold drawing
Branching decreases crystallinity
Crosslinking prevents crystallinity
Crystallinity affects polymer properties, but, unlike small molecules, poly-
mers are not completely crystalline. A basic requirement for crystallinity is
regularity of the chain structure. Regularity allows proper alignment of
polymer chains so that crystallization can occur. Noncrystalline regions in
polymers are called
. Regularity can be increased by stretching
and cold drawing, because this lines up the molecules. Because branching
inhibits regularity, branched polymers tend to be less crystalline. Crosslink-
ing prevents polymers from orienting to achieve the regularity required for
crystallization.
amorphous
