When a polymer melt is cooled slowly: spherulites

1
MORPHOLOGY

• When a polymer melt is cooled slowly
  spherulites
• (roughly spherical, semi-crystalline structures)
  form.
• Spherulites begin to grow from various nuclei
  in a radial fashion until they hit each other
  (form interspherulitic boundaries).
• Spherulites Consist of
• Nucleus (Nucleation Site)
• 2. Lamellar Fibrils
• -bundles or stacks of chain folded crystalline
  lamellae/crystallites
• - flat and ribbon-like diverge, twist, and
  branch as they grow from nucleus
• 3. Amorphous Tie Chains
• -connect individual lamellae (add strength)
• - tie chains form amorphous regions

Lamellae (crystallites) ? Tm Amorphous Chains ?
Tg (no Tm)
2
Portions of polymer chains align by chain
folding to form crystalline lamella (i.e.
crystallites) (exhibit a Tm )
chain folded crystalline lamellae
Amorphous Tie Chains
Lamellar fibril
Amorphous tie chains (exhibit a Tg)
Purely amorphous polymers lack crystalline
lamellae (i.e. they are not semi-crystalline) Thu
s, they do not exhibit a Tm.