Preparation And Properties Of Porous PLA Composites Based On FDM

Polymer porous material is a hot topic in the current research field of material science.However,it is difficult to realize the formation of complex structures and customized porous materials by conventional methods for polymer porous preparation.3D printing?3DP?has significant advantages in rapid prototyping of complex structures,personalized customization and shortening development cycle.Fused Deposition Modelling?FDM?is a typical 3D printing rapid prototyping process,which develops rapidly because of its low cost and simple equipment.However,the limited print accuracy of the FDM 3D printer makes it difficult to print the micron-sized and nano-sized pore structures.In order to solve the above problems,a new type of polylactic acid?PLA?-based FDM composites was prepared by melt blending extrusion method,and a new method for fabricating PLA-based porous devices by 3D printing-water washing?3DP-W?was explored.This paper focuses on two new PLA-based composite filaments,which prepared by modifying PLA with two types of water-soluble porogens:polyvinyl alcohol?PVA?and sodium sulfate?Na₂SO₄?,and composite porous devices prepared by 3DP-W method.The mechanical properties,thermal properties,processing properties,degradation properties and pore structure of the composites were tested and characterized by universal mechanical testing machine,synchronous thermal analyzer,thermal deformation temperature tester,MFR,XRD and SEM.Firstly,PVA/PLA porous composites with PVA as porogen were studied.The formula of composite was designed preliminarily,the extrusion temperature range was determined,and the effects of PVA content and toughening agent on the properties of porous composites were investigated.The results show that:the suitable extrusion temperature range was from 170?to 180°C;the addition of PVA increased the heat resistance,crystallinity and degradation performance of the composites;with the increase of PVA content,the porosity of composites increased,the tensile strength decreased slightly,and the fluidity and toughness decreased significantly.When the PVA content was 30wt%,the porosity of the device reached 23.1%,and the tensile strength of the composite was 51.61MPa,but the flowability and toughness were to be improved.Then,the composites were modified with four kinds of toughening agents such as PBAT,EVA,PEG and TPU,the elongation at break and the impact strength of the composites were improved after toughening.When the toughening agent content was 5wt%,the toughening effect was ranked as EVA>TPU>PBAT>PEG,and the flow improvement effect was ranked as PEG>PBAT>TPU>EVA,5wt%PBAT toughened PVA/PLA FDM composite filaments with good flexibility and uniform size,which meets the requirement of printing.Secondly,Na₂SO₄/PLA porous composites with Na₂SO₄ as porogen were studied.The effects of different Na₂SO₄/PLA mass ratios,toughening agents and plasticizers on the properties of the composites were investigated emphatically.The results show that:the addition of Na₂SO₄ improved the heat resistance,crystallinity and degradation properties of the composites;and the porosity of the composites increased with the increase of Na₂SO₄ content,but the strength,toughness and fluidity of the composites decreased.When the mass ratio of Na₂SO₄/PLA was 30/70,the porosity of the device was 25.9%,the tensile strength of the composite was 43.58MPa,the impact strength was 11.53kJ/m²,and the MFR was 3.62g/10min;the impact strength and MFR of the composites were increased to 14.45kJ/m² and 5.38 g/10min respectively by adding TPU as toughening agent and DINCH as plasticizer,the toughness and fluidity of the composites were improved.Besides,the effect of different ball-milling time on the porosity of porous composites was investigated.The results show that the optimum ball-milling time was 3 hours,the porous composites had high porosity and uniform pores.The 3D models were designed by 3D software,the models with complex structure were printed in the FDM 3D printer by using the above PLA-based composite filaments.Then,the water-soluble porogen in the device were removed by water washing,and the PLA-based devices with micron-sized pores were fabricated.The feasibility of preparing PLA based porous devices by 3DP-W method is verified,which has potential application value in filtration and adsorption.