HNTs Template Method To Prepare Carbon Nanomaterials And Its Application In PTFE

Polytetrafluoroethylene(PTFE)was widely used in the chemical industry because of its good chemical and thermal stability and low friction coefficient.However,it has the disadvantages of poor wear resistance,easy creep,poor mechanical properties,etc.,which greatly limits its application in various fields,so it needs to be modified.Carbon nanomaterials have excellent mechanical properties and can be used as fillers to modify PTFE,greatly improving its wear properties.However,materials such as graphene(GN)and carbon nanotubes(CNTs)are expensive,and single carbon nanomaterial cannot fully improve the mechanical and frictional wear properties of PTFE as a filler.Therefore,it is of great value to prepare carbon materials by simple methods and use their composites to fill PTFE.In this paper,a low-cost,green and simple method of preparing GN was proposed.Using halloysite nanotubes(HNTs)as a template,the coiled nanostructures were used to synthesize GN-HNTs complexes by intercalation in-situ polymerization with the introduction of a carbon source.GN can be obtained after removing the template.The XRD,FTIR and other characterizations proved that the polyacrylamide was successfully inserted into the interlayer of HNTs.XRD,TEM,HRTEM,SEM and other characterizations showed that GN was prepared.The synthesized GN consisted of micro-sized folds and folded nanoflakes.Raman and XPS showed that the prepared GN was highly graphitized.When PTFE was filled with GN and GN-HNTs,it was found that when the filler content was gradually increased,the tensile strength and elongation at break of the composites first increased and then decreased,and the elastic modulus of the material was significantly improved.The lowest value of the tensile strength of the composites filled with GN-HNTs was 17.25 MPa,and the lowest value of GN after filling was 27.82 MPa,which is not much lower than the pure PTFE tensile strength of 28 MPa.The elongation at break of pure PTFE was 490%,the elongation at break of GN-HNTs-filled PTFE can reach 280%at the lowest,and the toughness was maintained.However,the minimum elongation at break of GN-filled PTFE was only 182%,which indicated that GN was eunited in PTFE.The Young's modulus of the filled GN-HNTs was about 1.9 times that of pure PTFE,and the maximum Young's modulus after GN filling was about 1.7 times that of pure PTFE.When GN and GN-HNTs were filled with PTFE,it was found that when the mass fraction continued to increase,the friction coefficient of the composite first decreased and then increased,and the volume wear rate gradually decreased.And at high loads and low speeds,GN-HNTs filled composites have excellent friction reducing properties.When the filler content was 2wt.%,200N,200r,the volumetric wear rate of the composite was only 0.0009cm3/h,which was 1/622 of pure PTFE.This article used the tubular structure of HNTs as a template,PVA was used as a carbon source,a mixture of carbon nanotubes/carbon nanorods(CNTs/CNRs)were prepared,TEM showed that the product is a mixture of CNTs and CNRs,consisting of nanotubes with large aspect ratio and short nanorods.XRD,FTIR,Raman,BET,resistance tests and other characterization qualitatively studied the ratio of CNTs and CNRs in the mixture.As a result,it was found that the increase in the amount of filler and the scale-up test all resulted in an increase in the mass fraction of CNRs in the product.The optimum ratio of PVA and HNTs was 1:1,the prepared CNTs/CNRs had a specific surface area of 583.187 m2/g and a pore volume of 2.142 cm3/g.CNTs/CNRs were used to fill PTFE,when the filler content increased,the tensile strength and elongation at break of the composites first increased and then decreased,and the elastic modulus of the materials was significantly improved.The lowest tensile strength of CNTs/CNRs filled composites was 27.74 MPa,which was not significantly different from the pure PTFE tensile strength of 28 MPa.The elongation at break of pure PTFE is 490%,and when the mass fraction of CNTs/CNRs was 3wt.%,the elongation at break was still as high as 375%,indicating that its initial properties kept well.The Young's modulus of CNTs/CNRs after filling is about 1.9 times that of pure PTFE.When the mass fraction of CNTs/CNRs increased,the friction coefficient of the composite decreased first and then increased.As the force on the composite increased,the friction coefficient decreased.When the frictional speed of friction of the composite material increased gradually,the friction coefficient increased first and then decreased.Based on these,it can be concluded that the composite material obtained at high load and low rotation speed can have excellent friction reducing performance.As the filler content gradually increased,the wear rate of the composite gradually decreased.When the filler content was 3wt.%,200N,200r,the volumetric wear rate of the composite material was only 0.0008cm3/h,which was 1/700 of that of pure PTFE and achieved the best filling effect.