Study On Preparation And Ptc Behavior Of Graphene And Carbon Nanotube Composites

PTC material is very sensitive to ambient temperature.It is a new type of smart material.It is mainly used in over-current,over-voltage and over-heat protection of integrated circuits.As electronic products have become smaller and more compact,integrated,energy-saving,and lightweightsistivity,and higher PTC strength for PTC devices.In this dissertation,GNs with one-di,people have demanded smaller dimensions,lower room temperature remensional structure and carbon nanotubes with two-dimensional structure were used to fill high-density polyethylene.Using the synergy between the two,it provides a new technical approach for the preparation of flexible,small size,ultra-low resistance PTC devices.And provide the necessary basis for the application of scientific research.The main research content is as follows:Preparation of Carbon Nanotubes Filled with High Density Polyethylene Composites and Study on PTC Performance:PTC composites were prepared by melt-mixing method using high-density polyethylene(HDPE)and modified carbon nanotubes(CNTs)as the filler.The micro morphology of the composites was observed by scanning electron microscope(SEM),the effect of the PTC and the mechanical properties were investigated by thermistor RT curve tester and impact tester upon the effects of the content of CNTs.Results revealed that CNTs disperses better in the HDPE matrix;When the content of carbon nanotubes is 9.0 vol%,the room temperature resistivity of the composites is as low as 10~2?·cm and PTC intensity of 4orders of magnitude;After adding modified CNTs in the system,the mechanical properties of composites could obviously be improved.The impact properties of composites were improved 93%higher than pure HDPE,when the carbon nanotube content is 8.0 vol%.Preparation of GNs Filled with High Density Polyethylene Composites and Study on PTC Performance:PTC composites were prepared by melt-mixing method using high-density polyethylene(HDPE)and modified GNs as the filler.The micro morphology of the composites was observed by scanning electron microscope(SEM),The effect of modified GNs content on the thermal stability and tensile properties of the composites was investigated by a thermogravimetric analyzer and a tensile tester.The results show that when the volume fraction of GNs is 13.0 vol%,GNs is in the form of lamellar packing,which indicates that when the volume fraction of GNS is high,GNs tends to agglomerate in the matrix.After GNs modification,some oxygen-containing groups were added to the GNs surface,the six-membered ring structure of the GNs carbon atoms was destroyed,and the surface defects of the GNs were increased,so that the thermal stability of the composite material was reduced;Adding modified GNs to HDPE can significantly increase the PTC strength of composites and enhance the withstand voltage performance;The addition of modified GNs to HDPE can effectively improve the tensile strength of composites.Preparation of GNs and Carbon Nanotubes Filled High Density Polyethylene Composites and Study on PTC Performance:The second conductive filler GNs was introduced,based on the individual filling of high-density polyethylene with carbon nanotubes,When the volume fraction of conductive fillers(carbon nanotubes and GNs)was fixed at 9.0 vol%,the effect of changes in GNs content on the PTC effect of composites was studied.The distribution of carbon nanotubes and GNs in the matrix was observed by Scanning Electron Microscopy(SEM).The effect of changes in the content of carbon nanotubes and GNs on the mechanical properties of the composites was analyzed through a tensile tester and an impact tester.The thermal stability of carbon nanotubes filled with high-density polyethylene composites and carbon nanotubes and GNs co-filled high-density polyethylene composites was compared through a thermogravimetric analyzer.The results show that when the GNs/CNTs/HDPE composite material at around 130°C,the resistivity of the composites changes dramatically,resulting in PTC effect.For GNs/CNTs/HDPE composites,when the conductive filler(carbon nanotubes and GNs)was fixed at 9.0 vol%and the GNs content was 4.0 vol%,the composite PTC strength was the highest,reaching6.29.It is 60%higher than carbon nanotubes filled with high-density polyethylene alone(the PTC strength is 3.92 when the carbon nanotube content is 9.0 vol%).Using the complementarity between one-dimensional structure GNs and two-dimensional structure carbon nanotubes,they are filled together with high-density polyethylene,the PTC strength of the composite material can be significantly improved,and the withstand voltage performance was enhanced.Composites containing carbon nanotubes and GNs co-filled with high-density polyethylene decompose earlier than composites filled with high-density polyethylene alone,indicating that the thermal stability of the latter is lower than that of the former.When the conductive filler(CNTs and GNs)of the composite material was fixed at 9.0 vol%and the GNs content was 4.0 vol%,the tensile strength of the composite reached about 30.71 MPa,which was the highest.Compared with carbon nanotubes filled with high-density polyethylene alone,its tensile strength was improved by about 10%,and its impact strength is increased by about 52%.In this paper,HDPE was co-filled with GNs and CNTs.In this study,GNs and CNTs were co-filled with HDPE to investigate the effect of one-dimensional and two-dimensional structure complementation of GNs and CNTs on PTC performance.The rich and novel physics of GNs and CNTs were used to make ultra-low resistance PTC devices.Bring great possibilities.Theoretical analysis shows that the unusual electrical conductivity,thermal conductivity and flexibility of GNs and CNTs will bring new ways for ultra-low resistivity and good PTC effect of PTC device composites.