Glassy Polymer

Strictly, any amorphous polymer is glassy at temperatures below its Tg, but in practice a glassy polymer refers to those polymers which are in their glassy state at room temperature, thus to amorphous polymers with a glass transition temperature above room temperature, in contrast to rubbery polymers, which have a Tg below room temperature, and (semi-)crystalline polymers with a melting point above room temperature. Under particular circumstances also semi-crystalline polymers can become glassy after quenching, if the crystallization kinetics and the crystal nucleation rate are sufficiently slow to prevent crystallization upon rapid cooling. A typical example of such polymer is poly(ethylene terephthalate), PET. Glassy polymers are characterized by their high stiffness and amorphous non-crystalline structure. These properties make them size selective in their dense form and also mechanically sufficiently resistant to exist as porous flat film or hollow fibre membranes. Examples of the...