تسجيل الدخول

تسجيل

Linear Saturated Polyesters

المؤلف:  A. Ravve

المصدر:  Principles of Polymer Chemistry

الجزء والصفحة:  p412-413

2026-02-05

350

Linear Saturated Polyesters

The saturated polyesters that find commercial applications are mostly linear except for some specially prepared branched polymers used in the preparation of polyurethanes. The linear polyesters became commercially important materials early in this century and still find many uses in industry. The earliest studies reported condensations of ethylene, trimethylene, hexamethylene, and decamethylene glycols with malonic, succinic, adipic, sebacic, and ortho phthalic acids [6]. Later studies showed that such condensations yield high molecular weight compounds [44]. Nevertheless, these polyesters exhibit poor hydrolytic stability and are generally low melting. Subsequently, however, it was found that aromatic dicarboxylic acids yield polymers with high melting points and poly(ethylene terephthalate), which melts at 265C, is now an important commercial material. Physical properties of linear polyesters follow the general observation of the relationships between physical properties and chemical structures of polymers (see Chap. 2). Aromatic diacids andor glycols with aromatic rings in the structures yield polyesters with high melting points, while the aliphatic ones yield low melting solids or viscous liquids. In addition, hydrogen bonding, dipole interactions, polarizations, stiff interchain bonds, molecular symmetry or regularity, and the ability of polymeric chains to undergo close packing raise the melting points. Conversely, bulky side chains and flexible interchain bonds lower the melting points.