| Biodegradable polymers attracted more and more attention from people since the increasing deterioration of environmental pollution problems. Poly (butylene succinate) (PBS) is one of the most promising research direction of biodegradable aliphatic polyester, which possesses great biodegradability and controllable biodegradation velocity. So it can be applied in making plastics and films. But the low molecular weight, low melting point and weak mechanical property of common level PBS limited it in narrow application spectrums. While the Poly (butylene succinate-co-terephthalate) (PBST) is a novel biodegradable copolyester made by the modification of PBS, and can be characterized as a kind of polymer with both biodegradability from aliphatic polyester and physical processing abilities from aromatic polyester. So the study of performance and spinnability of higher molecular weight PBS and modified PBST will be considerable in purpose of developing the application in the field of biodegradable fibers.In this paper, the thermal properties, crystallization behaviors, rheological behaviors have been investigated, and the spinnability was elementarily exploited and the feasible spinning processing condition was proposed. Meanwhile, the basic performance characteristics of PBST were implemented. The thermal properties, crystallization behaviors, rheological behaviors were also carried out. The PBST fibers with certain tensile strength and satisfied for the weaving were successfully prepared in the laboratory, as the optimum spinning processing condition for PBST were brought up based above researches.First, the fundamental properties of PBS and PBST copolyester have been characterized, including macromolecular sequence structure, thermal properties, viscosity and empirical constants K, a. The results of ~1H HMR indicated that the molar ratio of butylene and succinate in PBS polyester was equal to each other. The molar ratios of BS to BT comonomer in PBST copolyester were about 30/70. Besides this, PBST copolyester has also been found that it was a kind of random copolymer. The results of DSC and TGA showed that the melt-point temperatures of PBS and PBST were 116℃and 181℃, that the crystalline-point temperatures of PBS and PBST were 66℃and 131℃, and that the crystallinities of them were 58% and 23.6% respectively, while the beginning thermal degradable temperatures are both around 380℃. According to the MHS equation, the empirical constants K, a could be calculated by the viscosities and molecular weights of different PBS or PBST samples. Then, study on the crystalline properties of PBS or PBST polyester is carried out by WAXD, DSC, POM and DLL The results of WAXD showed that PBS belongs to the single-inclined crystal system and PBST belongs to the triclinic crystal system. According to the non-isothermal crystallization kinetics and POM pictures, the crystalline morphologies of PBS and PBST are spherulite. The crystallization behaviors of PBS or PBST were attributed to both homogeneous nucleation and heterogeneous nucleation. And the dimensions of spherulite growth are also including two-dimension and three-dimension. Besides, the result of DLI revealed that the semi-crystalline time of PBS is the shortest one at 65℃, which also meaned that the whole crystalline velocity is the fastest. And the same rules happened in PBST at 90℃.In order to study the spinnability of PBS and PBST, the rheological properties were investigated with different PBS and PBST polyester samples. The results showed that, the apparent viscosity of PBS or PBST increased along with the increasing of shear rate, therefore they were typical non-Newtonian pseudoplastic fluid. The flow activation energy of PBS and PBST reduced as the shear rate increasing, so their sensibility of temperature reduced as well. When different PBS or PBST samples had the same shear velocity, the non-Newtonian index n increased following the temperature increasing. When the temperature stayed steadily, n decreased with the increase of shear rate. As the temperature boosted, structural viscosity indexΔηof PBS or PBST melt minished, but the thermal degradation increased. Under the same shear velocity, the higher the molecular weight was, the greater the shear stress a of PBS or PBST, apparent viscosityη_a andΔηincreased, but the smaller n became.The study on the spinnability of PBS and PBST during the melt spinning process represented that PBS just had passable property of melt spinnig, exhibited fragile property of its fibers and was hard to draw during the hot setting process. It is possibly related to the molecular weight of PBS polyester or the contained inner-water quantity. While PBST possessed the good spinnability, the range of take-up velocity was from 400m/min to 1000m/min. After PBST as-spun fibers were drew 2 times, the strength of PBST fibers could arrived at 3.47847cN/dtex, which meant that they could meet the application in the textile industry. The elasticities of PBS fibers and PBST fibers were also good enough and the water shrink ratio could reach 25%～30%.Finally, the study of PBS and PBST fibers degradation were carried on by the degradation experiments with the bioactive hydroponic sludge. The researches proved that: PBS fibers lost more weight than PBST fibers, which represented that the degradation rate of the PBS fibers were faster than that of PBST fibers. The SEM pictures clearly showed that eroded by microorganism and water molecules, the surface of the PBS or PBST fibers became rough. DSC data showed that the melting point and enthalpy of PBS or PBST fibers have an ascended trend when the time passed by, this may reflected that the degradation of polymers reacted firstly in amorphous area, or that the macromolecular of polymers might recrystallize. These results accorded with the WAXD results. Besides, mechanical properties of single fibers also reflected that after degradation the strength of PBS or PBST single fibers decreased, and it was clear proved that the degradation degree increased as the time passed by.
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