The Preparation And Fused Deposition Modeling Process Of Polylactic Acid/Organic Modified Montmorillonite Nanocomposite Filaments

As a new type of digital manufacturing technology,additive manufacturing technology,from computer CAD design to final parts molding,does not require dies.It can make any complex structure in a short time,which effectively shortens the product development cycle,improves the quality of the product and reduces the production cost.And fused deposition modeling(FDM)technology has simple equipment,clean process,low operating cost and no excessive processing residue.It has become the most widely used process.However,there are few kinds of materials suitable for melting deposition,mainly two kinds of thermoplastic plastics ABS and PLA.PLA is widely used because of its good biocompatibility and degradation of environment.However,because of its poor impact performanceand weak thermal stability,it can't meet the complexity of biological structure,which makes the performance of FDM forming parts Limited,and also restricts the wide application of FDM technology in the field of biological medicine.In view of the characteristics of FDM technology,the preparation of new polymer composites can be used as an effective way to broaden the range of FDM materials.It is an effective way to improve the comprehensive properties of FDM forming parts by combining the properties of natural inorganic fillers with unique mechanical and thermal properties with the toughness,machinability,corrosion resistance and wear resistance of polymer materials.Based on this idea,this paper prepared polylactic acid/ organic modified montmorillonite(OMMT)nanocomposites by melt mixing method,and then prepared PLA/OMMT nanocomposite filaments by single screw extrusion mechanism.The precision and mechanical properties of 3D printing samples were further studied by different content and molding process(printing direction in the angle of raster).The applicability of PLA/OMMT as a new type of FDM printing material was systematically evaluated.The main research results are as follows:(1)The properties of the composite filaments have a great relationship with the preparation process and the addition of OMMT,especially on the melting index and mechanical properties of the filaments.It is found that with the increase of OMMT doping,the melt index of the filaments decreases.At the higher screw speed,the fluidity decreased obviously when the doping amount was 1wt%.With the increase of the doping amount,the fluidity decreased and the fluidity decreased with the increase of OMMT doping at the lower screw speed.When the screw speed is at 8rpm,the doping content of montmorillonite is 1 wt%,and the material has suitable fluidity.The high or too low rotation speed and the doping content of montmorillonite will reduce the tensile strength of the prepared filaments.(2)The mechanical properties of PLA/OMMT nano composite FDM printing parts were analyzed.It was found that when the organic modified montmorillonite was doped with 1wt%,the tensile strength,the bending strength and the impact strength were improved to a certain extent compared to the pure PLA,but the microstructure was similar,and the OMMT was better for PLA.With the continuation of the doping content,the content of the organic modified montmorillonite was improved.At the same time,the printing process is affected by the viscous sintering dynamics,and the lower melt fluidity restricts the bonding between the filaments and forms a large number of micro pores,and the mechanical properties are obviously reduced.(3)Through the single factor experiment design,the surface roughness and molding precision of the PLA/OMMT nanocomposite FDM printing parts are analyzed.It is found that the process parameters have influence on the surface roughness and the forming precision of the forming parts with different OMMT doping content,and the number of the corresponding layer is less when the thickness is larger,which will reduce the addition.At the same time,smaller path width will cause more uneven nozzle speed,so it may lead to larger surface roughness.It is found that the sample with lower surface roughness can be obtained in the layer thickness of 0.2mm and the 0 degree direction and with the organic modified montmorillonite content as 1wt%.