Preparation Of Branched Polyester And Its Application To Improve The Spinnability Of Anti-pilling PET Fiber

Poly(ethylene terephthalate) (PET) fibers with anti-pilling performance is an important product. In the industry, low molecular weight PET is commonly used to produce anti-pilling fibers, however, its spinnability is poor and many efforts have been made to improve its spinnability. In the work, a branched PET was prepared by solid state polycondensation(SSP) from PET and pentaerythritol (PENTA), and the resultant PET-PENTA branched co-polyester was added into low molecular weight PET([η]=0.46) to improve its spinnability.In this thesis, the SSP process to prepare branched co-polyester was researched. The result showed that crosslinking could be avoided by controlling reaction time. When the PENTA content was above 0.8mol%, the intrinsic viscosity(IV) of PET-PENTA co-polyester slightly decreased and then increased with prolonging SSP time, while it maintained increasing if PENTA content was low enough. Higher PENTA content facilitated the form of branching structure . Then the structure and crystal performance of PET-PENTA co-polyesters with different SSP time are characterized by pol arizing microsc ope with hot stage and differential scanning calorimeter(DSC). The results showed that crystal morphology of the co-polyester changed, in the early period of SSP, the little spherulites of co-polyester was observed.While the co-polyester with longer SSP time formed little crystal. Meanwhile the crystalline rate of PET-PENTA was lower than that of pure PET.The blend spinning of PET-PENTA co-polyesters and PET with low IV was employed. Polarizing microscope with hot stage, DSC and scanning electron microscope(SEM) and other analysis methods were also used to study the compatibility and spinnability of PET and PET-PENTA. The results showed that the PET-PENTA co-polyester was compatible with the low IV PET. When the dosage of PET-PENTA was above 20%, the blend chips had good spinnability and the spinning temperature of the blend chips were lower than that of pure PET ([η]=0.64).The mechanical properties, hydrophility, thermal stability and dyeability were tested. The results showed the blend fibers had lower tensile strength and elongation to break, as well as enhanced initial modulus comparing to that of pure PET with the same drawing ratio. So the blend fibers met the requirements of anti-pilling fiber. In addition, the blend fibers showed excellent hydrophility, dyeability and thermal stability.