Preparation Of Cationic Dyeable Poly(Trimethylene Terephthalate) Fiber

Poly(trimethylene terephthalate)(PTT) has been introduced as a commercial polyester for textile fiber with outstanding combination properties. Although PTT fiber exhibits better dyeability than PET fiber, only disperse dyes can be adopted with high temperature and pressure, which limits the development of PTT fiber in our country. Easy cationic dyeable poly(ethylene terephthalate)(ECDP) containing -SO₃Na groups can be deep-dyed at atmospheric pressure and boiling condition, and its bright colors can meet the diversified needs of modern life. Therefore, blending PTT with ECDP to prepare cationic dyeable CDPTT fiber is an effective way to improve the properties, especially the dyeing property of PTT fiber.In this thesis, a series of PTT/ECDP blends were prepared in different blending ratio and blending technique. ¹³C-NMR was used to investigate the transesterification of PTT/ECDP blends. From the NMR data, the randomness parameters (B) were calculated to be less than 1, which shows that the blends resembled a block copolymer. The ester-exchange degree (f) and B of PTT/ECDP blends increased and number-average sequence length Ln_PT, Ln_ET reduced with ECDP content increased at the same blending temperature and time. The intrinsic viscosity decreased with increasing ECDP content when ECDP content less than 30wt%, but increased when ECDP content was above 40wt%.With the same blend ratio, f and B increased with increasing blending temperature and time, while Ln_PT, Ln_ET and the intrinsic viscosity decreased.The thermal properties and crystallization behaviours of the blends were investigated by differential scanning calorimetry thermograms (DSC) and hot-stage polarized optical microscopy (POM). The results showed that the melt crystallization temperature (T_mc) and the crystallinity degree (X_c) of the blends decreased with increasing ECDP content and blending time at the same blending temperature. With the same blend ratio and blending time, T_mc and X_c gradually reduced with increasing blending temperature. When the blending temperature increased further to 280℃, T_mc and X_c were slightly higher than those at blending temperature of 270℃, perhaps due to shorter chains resulting from further transesterification reaction and the thermal degradation of ECDP were easier to form a crystal. As the sequence length Ln_PT decreased, T_mc and crystallinity of the blends gradually reduced.Based on the research of melt rheological properties of PTT/ECDP blends, CDPTT fiber was prepared with PTT / ECDP (80/20 wt%). It showed that the breaking strength of CDPTT fiber decreased, as well as the breaking elongation and boiling water shrinkage increased with comparison of PTT fiber. The performances of CDPTT fiber can meet the requirements of textile.Dyeing experimental kinetics with cationic red SD-GRL for CDPTT fibers were studied. It found that the introducing of sulfonic groups has a great improvement on dyeing and CDPTT fiber can be deep-dyed at atmospheric pressure and low temperature. The dyeing rate of CDPTT fiber increased with the increasing dyeing temperature and dyeing time. When the dyestuff desorption and adsorption reached equilibrium, the dyestuff uptake would keep constant. Dyeing rate increased as the bath ratio decreased. It showed a rapid dyeing rate at the initial stage and was appropriate to reduce the dyeing temperature and increase the bath ratio when dyeing. The balance dyeing rate (C_∞),dyeing rate constant (k) and diffusion coefficient (D) increased, half-dyeing time (t_1/2) decreased with the increase of dyeing temperature.