Research On Structural Design And Conductive Properties Based On Biodegradable Composites

Conductive polymer composites(CPCs)are prepared from conductive fillers(such as carbon black,carbon nanotubes,graphene,metal particles,etc.)and polymeric matrices.In order to achieve the required conductive properties of conductive polymer materials,it is usually necessary to add more conductive fillers,which not only increases the difficulty of processing the composite material,but also impairs the mechanical properties of the material.Therefore,reducing the conductive filler content of conductive polymer materials and obtaining better conductive properties is an important research direction for polymer-based conductive composite materials.PLA,PBAT and superconducting carbon black were used to prepare a series of conductive composites by melting and mixing in this paper.The effects of different carbon black contents on the mechanical properties,dynamic thermodynamic properties,crystallization properties and conductive properties of conductive composites were studied.In addition,through the regulation of the microstructure of the conductive composites,the influence of the regulation of the microstructure of the conductive composites on its conductive properties was studied.PLA/CB conductive composites were prepared by melt blending of polylactic acid(PLA)and superconducting carbon black(CB).Universal tensile testing machine,dynamic thermomechanical analyzer,DSC,high resistance meter,SEM and other instruments were used to study the influence of different CB content on the mechanical,dynamic thermo-mechanical,crystallization and electrical properties of the blended composites and micromorphology of the composites.The results showed that the addition of 2.5 wt% CB makes the tensile strength of PLA/CB composite reach 76.6 MPa,which was better than that of PLA itself,but the elongation at break of the composite decreased from 19.7% to 9.8%.The initial storage modulus and crystallinity of the composites also increased with the addition of CB.The addition of CB increased the electrical conductivity of the composites.The relationship between conductivity and CB content of conductive composites was typical percolation behavior.The percolation threshold of the PLA/CB composites was 0.49 wt%.PBAT/CB conductive composites were prepared by melt blending of poly(butyleneadipate-co-terephthalate)(PBAT)and CB.Universal tensile testing machine,DSC,XRD and other equipments were used to study the effects of different CB content on the mechanical properties,crystallization properties,electrical properties of the blended composites and the microstructure of the composites.The results showed that the addition of CB maked the tensile strength and elongation at break of PBAT/CB composites worse,the tensile strength decreased from 21.5 MPa to 13.6 MPa,and the elongation at break decreased from 1851.2% to 621.9%.The addition of CB also reduced the crystallinity of PBAT/CB composites,but did not have much effect on the PBAT crystal structure.The conductivity of composites was improved because of the addition of CB.The relationship between the conductivity of the composite material and the CB content was a typical percolation behavior,and the percolation threshold of PBAT/CB conductive composites was 1.98 wt%.PLA/PBAT/CB conductive composites were prepared by the internal mixer of PLA,PBAT and CB.The selective distribution of CB in composites was predicted from a thermodynamic point of view.The effect of different PLA and PBAT composition ratios(certain CB content)on the microstructure and electrical conductivity of the conductive composites was investigated by means of high resistance meter,SEM,and polarized light microscope.It was found that when the composition ratio of PLA and PBAT was 1:1,the conductive composites formed a co-continuous microstructure.In order to study the relationship between the co-continuous structure of PLA/PBAT/CB composites and CB contents,we prepared a series of conductive composite materials with different CB contents and PLA/PBAT composition ratio of 1:1.Through the high resistance test,it was found that the relationship between the conductivity of the co-continuous structure of PLA/PBAT/CB composites and the CB contents still belonged to classical percolation behavior,and the percolation threshold of the co-continuous structure of the conductive composites was reduced to 0.42 wt%.Below the percolation threshold of PLA/CB and PBAT/CB conductive composites.At the same time,we also explored the effect of changing the order of blending of PLA,PBAT,and CB on the electrical properties of the system,and found that changes in the order of blending additives had a certain influence on the conductivity of the material.