Aromatic polyesters solubility characteristics

Solubility tests permit at least a tentative identification of the components also in polymer blends. Blends of ABS and polycarbonate are soluble in most polar solvents. Solubility in tetrahydrofuran and methyl ethyl ketone demonstrates the absence of polyolefins in such blends and the presence of aromatic polyesters or of polyamides can also be excluded. On the other hand, generally they may contain such highly soluble polymers as polystyrene, PVC, ABS, or polymethacrylates. However, blends that contain polybutylene terephthalate or polyethylene terephthalate do not dissolve in the usual solvents, but require m-cresol, which can he a clear indication that aromatic polyesters are present. Polyolefins dissolve at high temperatures, at least 110 °C, in toluene and p-xylene, and this behavior is characteristic of blends that contain polyethylene or polypropylene. 

The same structural modification concepts, which were utilized to modify the properties of para-linked aromatic LC polyesters, have also been applied to aromatic polyamides. Para-linked aromatic polyamides are an important class of LC polymers. In contrast to thermotropic LC polyesters, para-linked aromatic polyamides form lyotropic solutions. Due to the formation of intermolecular hydrogen bridges, these polymers are in most cases unable to melt below their thermal decomposition temperature. Infusibility and limited solubility of unsubstituted para-linked aromatic polyamides are characteristic properties which limit synthesis, characterization, processing, and applications. 

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