Semi-crystalline polymer.

A semi-crystalline polymer has crystalline regions (usually in the form of spherulites) and amorphous regions.

There is local folding of linear chains causing the appearance of lamellae made of cubic, orthorhombic or hexagonal cells.

Thermoplastic polymers are either amorphous or semi-crystalline. The crystallinity rate varies from 20% to 80% depending on the product.

For example, PEEK (polyether ether ketone) is 30% crystalline and 70% amorphous.