Thermal and Mechanical Properties of Halogen-Containing Aromatic Polyamides

Abstract

Aromatic polyamides containing fluorine, chlorine, bromine and iodine have been prepared, and they have been evaluated by their mechanical and thermal properties. The method of polycondensation in solution at low temperature revealed as a very appropriate route to attain high molecular-weight halogen-containing polyisophthalamides (PIPA's) from aromatic diamines and 5-halogenoisophthaloyl chlorides. High glass transition temperatures (Tg) were found for the set of polymers, in the range 250–350°C, showing a clear dependence on the size of the halogen incorporated, with values of Tg growing up in the series F < Cl < Br < I. On the other hand, thermal resistance was slightly impaired by the presence of halogens, as revealed by thermogravimetric analysis (TGA). In the same way, the mechanical strength was poorer than that of the parent unmodified PIPA's, by about 20%. All the polymers exhibited a mechanical relaxation at sub-ambient temperature, about –70°C, associated to local molecular motions involving halogen atoms.