ABSTRACT
Thermoplastic materials gain their characteristic properties because of their ability to crystallize from the melt (liquid, amorphous) phase into semicrystalline solids. Unlike metals, thermoplastics do not achieve 100% crystallinity; hence the term, semicrystalline. Morphologically, semicrystallinity in polymers is attributable to the presence and occurrence of lamellae. Lamellae occur because of the folding of polymer chains. Transmission electron microscopy (TEM) micrographs [1-4] of single polyethylene crystals indicate that the folded chains appear mostly on the surfaces of the lamellae, whereas the interior is made up of long-range, ordered chain stems. Lamella length can be up to 100 μm, and thickness is less than 30 nm. Figure 6.1 is a sketch of a typical semicrystalline polymer.
