The Structure of Solids

· When crystals of polyethylene are grown from a melt of the material, reduced molecular mobility causes the solid to have both crystalline and amorphous regions.
· The macromolecules of Poly-ethylene extend through many of the Orthorhombic unit cells and also into amorphous regions of the solid.
· This "composite" structure obtains its strength from the crystalline regions and its flexibility from the amorphous zones.

From: Cotterill, "The Cambridge Guide to the Materials World," Cambridge (1989)