| PTT fiber is getting more and more widely used in carpets and garment field because of its excellent general performance. However, its non-achievement of mass production inland caused its stiff price and importation in a great measure, which limited its application. PBT has already been produced and applied in China, but as fiber, PBT fiber is not as good as PTT fiber in recovery, breaking elongation, dimensional stability and so on.Due to the comparability in configuration and melting point of PTT and PBT, it is expected that a type of novel polyester fiber with better general performance than PBT fiber and close to PTT fiber could be obtained by blending PTT and PBT together.In this paper, DSC, WAXD, SEM, POM and torque rheometer were used to research on the compatibility, crystalline behavior and rheological property of PTT/PBT blends, alloy fibers were then prepared based on the data, and general mechanical properties, recovery, heat shrinkage and dyeability were finally measured and discussed. The results are as follows:DSC, WAXD and SEM results showed that PTT/PBT blends were miscible in amorphous region, but phase separated in crystal region, a diphase system with tiny phase domain overall. T_g values predicted the heat roller temperature to be around 68℃when drawing the spun-fiber, and the fibers could be dyed under atmosphere with disperse dyes. T_m values of PTT and PBT were so close which indicated that the spinning process might be easy to control, with the predicted spinning temperature of 250-275℃. Melt crystallization behavior, crystal morphology and crystallization kinetics for PTT/PBT blends were studied via DSC and POM methods. The results indicated that when PBT component was above 20%, the existence of PBT promoted the cold crystallizability of the blends. While during the melt crystallizing process, the addition of a second component restrained the crystallization of the system. The blends crystallized in three-dimensional way into spherical crystals, and both homogeneous nucleation and heterogeneous nucleation existed.The rheological behavior of the blends indicated that the blends were typical pseudoplastic fluids. The apparent viscosityη_a fell with the increasing PTT content, and got a maximum when PTT content was 50%. The non-Newtonian index n got the minimum when PTT content was 50% and got the maximum when PTT content was 30% and 70%. With the increasing PTT content, the viscous flow activation energy E_ηfirst grew and then fell, got the highest when PTT content was 70%, which was the most sensitive to temperature. It was also found that E_ηvalue was relatively high when the shear rate was too high or too low, which resulted in the controlling difficulty in spinning process.PTT/PBT blends behaved excellent melt spinnability. PTT content obviously improved the stretchability of the fiber. With the increasing PTT content, the strength of the fiber first fell and then grew. Though the higher spinning speed resulted in higher strength of the fiber, the inhomogeneity of mechanical properties was caused at the same time. When 20% of test elongation was set during the recovery measurement, the alloy fibers with PTT content above 50% behaved much better recovery than pure PBT fiber, and quite close to the recovery of pure PTT fiber when PTT content was above 70%. It is worth mentioned that when the test elongation was 15%, alloy fibers with PTT content above 50% could even reach 100% of recovery. When all the fibers were drawn at the same times, alloy fibers with PTT content above 50% could improve the dimensional stability of the system. Dye-uptake of the alloy fibers were higher than that of the pure ones, and got the highest when the mass ratio was 50/50. All the experiment results indicated that alloy fibers with PTT content above 50% could be used instead of pure PTT fiber. |
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