New Plastics as Heat Resistant Polymers.

Whereas the heat deflection temperature of crystalline polymers is linked to their melting points, that of amorphous polymers is linked to their glass transition temperatures. This results in the demand for high crystalline order and/or low melt entropy. For the familiar plastics to be modified, these requirements can be met by means of higher crystallinity, higher secondary valency forces or voluminous side groups. With the more recent plastics the approach is chiefly via stiff aromatic chains or condensated rings. The demand for thermal stability also calls for the materials having adequately high molecular weight to obtain valuable performance properties. The following materials are described as single-bond, aromatic chain polymers: polyalkylene terephthalate (polyethylene terephthalate, polybutylene terephthalate), polysulfone, polyphenylene sulfide, polyaryl sulfone, polyether sulfone, polyaryl ether; aromatic polyhetereocyclics (semiconductor polymers): polyamide, polyamide imides, poly-bis-maleimides, polybenzimidazole; single-bond polyheterocyclics: polyhydantoins; aromatic conductor polymers: polyimidazopyrolone (Pyron), cyclized polybutadiene (Pluton).