Journal of Applied Polymer Science, Vol.86, No.5, 1278-1284, 2002
Synthesis, characterization, and thermal properties of phosphorus-containing, wholly aromatic thermotropic copolyesters
A series of phosphorus-containing, wholly aromatic thermotropic copolyesters from acetylated 2-(6-oxide-6H-dibenz<1,2>oxa phosphorin-6-yl)-1,4-dihydroxy phenylene, p-acetoxybenzoic acid, terephthalic acid, and isophthalic acid were prepared by melting polycondensation. The structure and basic properties of the polymers, such as the glass-transition temperature (T-g), melting temperature (T-m), thermal stability, crystallinity, and liquid crystallinity, were investigated with Fourier transform infrared, elemental analysis, differential scanning calorimetry (DSC), thermogravimetric analysis, wide-angle X-ray diffraction, and hot-stage polarizing optical microscopy. The copolyesters had relatively high T-g values ranging from 183 to 192degreesC. The T-m values obtained from DSC curves for samples P-20 and P-25 were 290 and 287degreesC, respectively (where the number in the sample name indicates the molar fraction of the phosphorus-containing monomer in the reactants). The initial flow temperatures of other samples observed with hot-stage polarizing microscopy were 271-290degreesC. The 5% degradation temperatures in nitrogen ranged from 431 to 462degreesC, and the char yields at 640degreesC were 41-52%. All the copolyesters, except P-40, were thermotropic and nematic.
Keywords:flame retardance;differential scanning calorimetry (DSC);glass transition;thermogravimetric analysis