Abstract: In this article, the solid-state polycondensation (SSP) of aromatic copolyester with low molecular weight was studied to prepare aromatic copolyester fiber with high strength and high modulus. Their rheological properties before and after SSP were analyzed. And the melt-spinning experiments of aromatic copolyester were operated. It is shown that SSP can increase the molecular weight greatly. Rheological analysis showed that the aromatic copolyester melt was a typical non-Newtonian fluid that exhibited shear thinning behavior. The apparent viscosity decreased and non-Newtonian index increased with the increasing of the temperature. The as-spun fiber with sample after SSP had higher strength than one before SSP. SEM images showed that the aromatic copolyester fiber is composed of macrofibril with 5 μm and fibril with 1μm.

Key words: aromatic copolyester fiber , solid-phase polymerization , melt-spinning , rheology