Study On The Preparation And Properties Of Poly（lactic Acid）/Fe₃O₄ Magnetic Melt-blown Nonwoven Materials

Nowadays,the widely used raw materials for the melt-blown（MB）nonwoven materials are some petroleum based materials,these products are difficult to be recycled and degraded when abandoned.With the development of the PLA as the raw material used for melt-blowing process and the advantage of excellent biodegradability and biocompatibility of PLA,it supplies an effective and feasible way to solve this problem.By means of compositing with some functional inorganic particles,PLA could be modified,which can also provide a new method to obtain the high value-added PLA based composites and MB nonwoven materials.As one kind of the functional inorganic particles,Fe₃O₄ has the characteristics of superior magnetic responsiveness,nontoxic and inexpensive,the existing studies on the magnetic PLA material are mostly used as medicine carrier,microwave absorbing materials,and so on.However,the application area in melt-blown material for air filtration has not been explored ever.Thus,this paper is aimed to lay the theoretical foundation for the research and development of magnetic PLA functionalized MB nonwoven materials for air filtration.In this paper,in order to improve the interfacial compatibility between PLA phase and Fe₃O₄ phase,Fe₃O₄-g-PLLA was prepared by grafting PLLA chains onto the Fe₃O₄ surface via the ring opening polymerization method,and then blended with PLA resin to obtain the PLA/Fe₃O₄-g-PLLA composite masterbatch with different mass ratio by using melt-blending processing.The thermal,crystallization and rheological properties of the blends were systematically investigated to provide some reasonable processing parameters for the melt-blowing processing.Finally,the thermal-crystallization,morphology,pore size distribution,permeability and filtration performance,mechanical and magnetic properties of the prepared melt-blown nonwoven materials were studied in detail.The conclusions were shown as follow:1.For the material obtained by the ring opening polymerization,its chemical constitution and crystal structure were characterized by Fourier transform infrared（FTIR）,Nuclear magnetic resonance（¹H-NMR）and X ray diffractometer（XRD）,all of the results illustrated that Fe₃O₄-g-PLLA particles were successfully prepared via the ring opening polymerization.The thermal weight loss range of PLLA in Fe₃O₄-g-PLLA particles was about 275-350℃,and its melting temperature was near 164.38℃.The scanning electron microscopy（SEM）and particle size analysis showed that the shape of Fe₃O₄-g-PLLA particles was roughly like"ball"and the average particle size was smaller than that of pure Fe₃O₄.Magnetic performance（VSM）testing exhibited that though the saturation magnetization of the Fe₃O₄-g-PLLA particle was lower when compared with pure Fe₃O₄,it still had good magnetic response.2.For the PLA/Fe₃O₄-g-PLLA composites,SEM indicated the Fe₃O₄-g-PLLA particles were uniformly dispersed in the PLA matrix,and the interfacial compatibility with PLA matrix was improved.The crystal structure and thermal properties testing of the composites revealed that the addition of Fe₃O₄-g-PLLA particles obviously hindered the cold crystallization process of PLA,but it didn’t change its crystalline structure.The thermal weight loss range of the composites was approximately 320-395℃.Through the discussion of the rheological properties of the composites,it stated that with the content of Fe₃O₄-g-PLLA loading,the complex viscosity of the composites increased,while their melt flow performance decreased.However,it still could ameliorate the flow property of the materials by appropriately increasing the processing temperature,and the suitable temperature for the melt-blowing process was 210-230℃.3.For the PLA/Fe₃O₄-g-PLLA melt-blown nonwoven materials,when the content of Fe₃O₄-g-PLLA increasing,the crystallinity of the melt-blown materials were declined,the fiber diameter of the materials were larger,the fiber surface became slightly rough,the pore size distribution of the fabrics turned wider,and their pore size got larger.Though the change of filtration performance was not notable,the permeability of the nonwoven webs improved and the filtration resistance reduced obviously.Tensile tests indicated that the tensile strength and elongation at break of the melt-blown materials increased first and then decreased with the content of Fe₃O₄-g-PLLA adding,which can achieve their maximum value when the amount Fe₃O₄-g-PLLA reached 1wt%.The acquired melt-blown materials were also endowed a bit magnetic response after the melt-blowing processing.