Amorphous plastics and crystalline plastics

Amorphous plastics and crystalline plastics

Oct 29, 2018

Many plastics are completely amorphous, such as: all thermosets; polystyrene and its copolymers; and polymethyl methacrylate.

However, some plastics are partially crystalline and partially amorphous in molecular structure, giving them both a melting point, the temperature at which the attractive intermolecular forces are overcome, and also one or more glass transitions, the temperatures above which the extent of localized molecular flexibility is substantially increased. These so-called semi-crystallineplastics include: polyethylene, polypropylene, polyvinyl chloride, polyamides (nylons), polyesters and some polyurethanes.