Structure And Properties Of PLLA/PBS Blends And Fibers

Poly(L-lactic acid)(PLLA) has already attracted extensive attention due to the excellent biodegradability, biocompatibility, mechanical property and good processability. However, its poor toughness and slow crystallization rate greatly restrict the application. The modification of PLLA with its good property maintained at the same time is an optimum method to expand its application. Polybutylene succinate(PBS) can be used in the modification of PLLA considering the good biodegradability and toughness. In this dissertation, Zinc acetate(Zn(OAc)2) was added into the PLLA/PBS blend as compatilizer. Based on the discussion of the relationship between structure and properties of the PLLA/PBS/Zn(OAc)2 blend, the spinnability and the blend fibers were further investigated. The main work and conclusions are summarized as follows:(1) The PLLA/PBS/Zn(OAc)2 blends with different blending ratios were prepared by melt blending. The morphology, crystallization behavior and mechanical properties of the PLLA/PBS/Zn(OAc)2 blends were investigated. The results show that the PLLA/PBS blends are incompatible and exhibit phase-separated morphology. With small amount of Zn(OAc)2 added in the blends, especially 0.05wt%, the PBS domain size decreases indicating that the compatibility between PLLA and PBS is improved. In addition, the crystallization rate and crystallinity of PLLA are effectively enhanced under the effect of PBS. The impact strength and elongation at break(above 300%) of the PLLA/PBS blends increase with increasing PBS content compared with those of pure PLLA. The PLLA/PBS/Zn(OAc)2=80/20/0.05 blend shows the best mechanical property.(2) The PLLA/PBS blend fibers were prepared by melt spinning. The relationship between structure and properties of fibers was investigated. The results show that the spinnability of blends and tensile strength of fibers decline with the content of PBS increasing. The tensile strength of fibers increase after adding the nano-TiO2. The tensile strength and the elongation at break of the PLLA/PBS/TiO2(95/5/1) fiber with drawn ratio of 3 are about 2.6cN/dtex and of 57% respectively. PLLA and its blend fibers with drawn ratio of 2 have highly crystalline orientation and shrinkage rate less than 10% in the boiling water. Besides, the addition of PBS improves the dyeing properties of the blend fibers. In addition, the fibers can be easily degraded in alkali liquor with the maximum weight loss of 35% after soaking in alkali liquor for 50 days at 37 oC.