Preparation And Properties Of A New Type Of PLA-based FDM Conductive Composite Material

Due to the small investment,easy operation and other specialties,the fused deposition molding?FDM?3D printing technology has been developed rapidly.However,the lack of 3D printing materials has become a bottleneck restricting the development of the industry.Most polymers are not conductive and fewer FDM filaments can be used in 3D printing conductive devices.Therefore,conductive polymer materials have been become the focus of current research.It is a good theoretical and practical significance to develop high value-added FDM conductive polymer materials.In this paper,the preparation and properties of two new types of PLA-based FDM conductive composites were investigated.This paper focused on the properties effective of different conductive agents within PLA-based FDM conductive composites,named GNPs/PLA and CF/PLA wood-plastic conductive composite filaments.The PLA-based composite filaments were prepared by single screw melting blend extrusion,and then personalized conductive devices were obtained by FDM 3D printer.The properties of the composite materials were tested and characterized by universal testing machine,TG,MFR,SEM and resistance meter,etc.Firstly,the conductive composites named GNPs/PLA was studied.The process condition of preparing GNPs by microwave expansion was studied.The effects of GNPs content,type and content of reinforcer on the electrical conductivity and mechanical properties of the composites were mainly investigated.The results show that:multi-walled carbon nanotubes?MWCNTs?and carbon fibers?CF?modified by coupling agent KH550 could improve the compatibility,extrusion properties and 3D printing properties of the composites.When the contents of GNPs,MWCNTs and K-CF in the composites were 0.4 wt%,0.4 wt%and 2 wt%respectively,the conductivity could reach 10^-4 S/cm,which was 10 orders of magnitude higher than that of pure PLA.The degradation rates of the three composites were ordered as follows:GNPs/K-MWCNTs-CF/PLA>GNPs/MWCNTs/K-CF/PLA>GNPs/MWCNTs/CF/PLA>pure PLA,the contact angles were in reverse order,which could explain the experimental results of composite degradation.Secondly,the CF/PLA/wood plastic composite was studied.The effects of CF content,KH550 modified wood flour?K-WF?content,flexibilizer type and content on the properties of the composites were investigated,then the suitable formula of composites was determined.The results show that:with the increase of carbon fiber content,the electrical conductivity,heat resistance,tensile modulus,impact strength and elongation at break of the composites increased,while the tensile strength decreased,and the bending strength first increased and then decreased.When CF content was 10 wt%,the conductivity of CF/PLA composite reached 10^-44 S/cm,and the MFR was 6.49 g/10 min.When K-WF content was 10wt%,the tensile strength and bending strength of CF/PLA wood plastic composites were 44.64 MPa and 74.40 MPa,respectively,while the impact strength and elongation at break were reduced.The preferred flexibilizer was polycaprolactone?PCL?.When PCL content was 6 wt%,the CF/K-WF/PLA wood plastic composite had moderate fluidity,good toughness,biodegradability and met the requirements of green and environmental protection.