Polymer constitution and fiber properties

Abstract

The chemical structure of a large number of linear condensation polymers is correlated with their ability to assume a polycrystalline form possessing the right degree of thermal stability, and with the possession of fiber‐forming properties. Certain structures lead to the absence of crystallinity and of fiber‐forming properties, while, under certain conditions, a low degree of crystallinity or its complete absence leads to polymers possessing rubberlike properties, which may form highly elastic threads. Some properties of fibers such as solubility, sensitivity to mositure, and certain dyeing characteristics, can be correlated to some extent with chemical structure. These effects are considered on the basis of the introduction of various polar links and ring structures, according to regular patterns, into the polymethylene chain (polythee). The ehter (RO) and ester (CO·O) links lower the crystallite melting point to such an extent that some polymers containing them are completely noncrystalline at normal room temperatures. Urethan (O·CONH), amide (CO·NH) and urea (NH·CO·NH) links raise the crystallite melting point to an extent which increases in the order named. Most other polar links raise the melting point. The introduction into the aliphatic chain of ring structures, particularly aromatic rings directly attached to polar groups, raises the crystallite melting point, but in this case symmetry exerts an over‐ruling effect. A low degree of symmetry may lower the melting point and even eliminate crystallinity entirely to the detriment of fiber‐forming properties. Inert side chains lower the melting point considerably, and in some cases render the polymer completely noncrystalline at normal room temperatures.