Km. Abdullaev et al., PHASE-TRANSFORMATIONS IN COPOLYESTERS BAS ED ON POLY(ETHYLENE-TEREPHTHALATE) AND HYDROXYBENZOIC ACID, Vysokomolekularnye soedinenia. Seria A, 39(5), 1997, pp. 842-847
Phase transformations in copolyesters between poly(ethylene terephthal
ate) and para-hydroxybenzoic acid, having various characteristic visco
sities and different ratios of the flexible and mesogenic fragments, w
ere studied by method of X-ray diffraction. The X-ray diffraction patt
ern of a copolymer with minimum viscosity exhibits an are-like feature
with increased scattering intensity against the amorphous scattering
background having the shape of the Debye ring. As the the temperature
increases, the texture first vanishes and then spontaneously appears a
gain at 250 degrees C, with the ''new'' texture axis making an angle o
f about 30 degrees with respect to the initial direction. The domains
of existence of a two-phase structure (local crystallites in a nematic
matrix) and homogeneous (nematic) structures in the copolyester melt
were determined. The effect of the phase state of melt on the mechanic
al properties of extruded copolyesters was studied.