Study On The Modification Of Polyester With Trace Of Additive

In recent years, large-capacity polyester direct spinning filament has developed rapidly due to its short process, efficiency, energy-conservation and stability. Because of the large economic scale and advanced technology, it is very popular with the investors. However, direct spinning of large-capacity polyester has single species; some enterprises consider online trace modification without affecting the spinnnability of polyester or alteration of the equipment. To optimize product, the direction of large capacity polyester is large capacity, low cost, direct spinning, flexibility and multi-variety.In this subject, trace modification agent was added to modify the property of polyester. So-called trace is the content of the modification agent≤3wt%, without affecting the efficacy of processing.In this thesis, first, aliphatic polyester polyhydroxyalkanoates (PHA) with good degradable performance was adopted to blend with polyethylene terephthalate (PET) for melt spinning. A series of PET/PHA blend fibers were prepared. The spinnability of the PET/PHA blends in the spinning process was investigated. It was found that there was no distinct difference between the spinnability of PET/PHA blends and PET at the amount of PHA added lower than 1.5wt%.The spinnability got worse when the amount of PHA added to 2.5 wt%, and the melt mobility of PET/PHA blends increased. The thermal properties of blends were studied by differential scanning calorimetry (DSC) and thermal gravimetric analyzer (TGA).The results showed that the melting temperature(Tm) of blends essentially unchanged, the melt crystallization temperature (Tmc) and the crystallization rate decreased with the PHA content increasing. The crystallinity degree (Xc), orientation degree and orientation factor (fs) of the blends fiber decreased with increasing PHA content obtained by X-ray diffraction. The moisture absorption and maximum draw ratio of blend fiber increased, the tensile strength of blend fiber decreased. The structure of blend fiber was studied by IR and NMR spectra. The results showed that there was transesterification occurred between PHA and polyester, which indicated the PHA flexible chain segments was introduced in the structure of blend.The degradation including mass degradation and degradation of breaking strength of blend fiber measured by Phosphate Buffered Saline (PBS) with different pH values. Test results showed that, the degradation of blend fiber got better with the addition of PHA. The maximum mass degradation and breaking strength degradation of blend fiber occurred at PHA content of 2.5 wt%. The etching of blend fiber surface became worse with the adding of PHA and degradation time.The PET/BaSO4 composites were prepared by two-step melt blending process and the dispersions of three different kinds of BaSO4 in the PET matrix were observed by scanning electron microscopy (SEM). The results showed that the aggregate extent of BaSO4 in the polymer matrix increased as the BaSO4 contents increased. The crystallization behaviour of the composites were studied using differential scanning calorimetry (DSC), The results showed that BaSO4 acted as nucleating agents during the crystallization of the PET matrix and improved the crystallization temperature and the crystallinity. The thermal gravimetric analysis indicated that the thermal stability of PET/BaSO4 composites increased with the increased further loading until the 2.5% loading. The rheology behavior of the PET/BaSO4 composites was measured using rotational rheometer (ARES-RFS) in a dynamic mode. It was found that the storage modulus (G'), the loss modulus (G") and dynamic viscosity of composites decreased with the introduction of BaSO4. Bnd PET/BaSO4 composites exhibited shear-thinning non-Newtonian fluids behavior as the same as PET.Traces of pentaerythritol (PER) was added with PTA, EG for copolymerization. A branched structure was formed with introduction of the structure of PER to the chain of polyester macromolecule, which would reduce the viscosity and improve the flow properties and spinnability of polyester. It showed the decrease in intrinsic viscosity of co-polyester measured by Ukraine viscometer at both PER content of 0.05wt%and 0.1 wt%. The melting temperature Tm was essentially unchanged and the melt crystallization temperature (Tmc) was decreased with the adding of PER. TG curve showed that the initial decomposition temperature of co-polyesters was no distinct difference, but the decomposition rate of co-polyester is faster than pure PET. The IR and NMR spectra showed that the chain segments of PER were introduced in the structure of PET, and branched-chain structure was generated. Through the test results of capillary rheometer, it was found that the curve of shear stress and shear rate of co-polyesters was downward, while melt mobility changed better and the Newton index of co-polyesters decreased for PER content of 0.05 wt%and 0.1 wt%.