Multi-walled Carbon Nanotubes Reinforced Polyamide 6 And Polyamide 66 Fibers Are Prepared And Characterized

In order to promote the application of the polyamide 6(PA6)and the polyamide 66(PA66)in the fields of the automotives,industry,etc.,and the application to the state-of-the-art technologies for the automotive tire cord,rope,etc.,in particular,the mechanical properties need to be further improved.The combination of the excellent mechanical properties,high electric and thermal conductivity has driven multi-walled carbon nanotubes(MWNTs)to be promising nanofillers in polymer nanocomposites.However,the strong van der Waals forces and large aspect ratio usually cause the severe agglomeration of the MWNTs,which limited its application.This is the problem that needs to be addressed by finding a solution that can evenly disperse the MWNTs and improve the interfacial interaction between the MWNTs and the polymer matrix.In order to obtain a better dispersion and a stronger interfacial interaction of MWNTs in PA6 and PA66 matrix in the process of melt spinning,the PA6/MWNTs-COOH and PA66/surface-modified MWNTs composite fibers were fabricated via a ball milling and melt spinning method.Firstly,PA6/MWNTs-COOH nanocomposite fibers were fabricated via a ball milling and melt spinning method.Transmission electron microscopy(TEM),Raman spectroscopy and X-ray diffraction were used to study the microstructure of MWNTs-COOH after ball milling.The effects of both the milling time and MWNTs-COOH loading on the mechanical properties and thermal properties of PA6/MWNTs-COOH nanocomposite fibers were also investigated.The experimental results demonstrate that the length of the MWNTs-COOH are decreased and end tips are gradually opened with increasing ball milling time,the ball milling process created new defects on MWNTs-COOH and preserved the crystal structures of MWNTs-COOH.The best dispersing time was 3 h.Compared with the traditional wet or melt spinning,the method of the ball milling and melt spinning makes the M WNTs disperse more uniformly in nanocomposite fibers,which can increase the utilization ratio of MWNTs,a maximum tensile strength is achieved at a loading of 0.1 wt%MWNTs-COOH in PA6,the tensile strength is increased by up to 67%and the Young's modulus is 91%higher compared with pure PA6 fibers.Moreover,the incorporation of MWNTs-COOH into PA6 improves the thermal stability.Secondly,PA66/MWNTs nanocomposite fibers were fabricated via a ball milling and melt spinning method.The microstructure and dispersability of MWNTs after ball milling were studied,and the effects of unmodified MWNTs(U-MWNTs),acid-modified MWNTs(MWNTs-COOH)and salt of dodecyl benzenesulfonic acid sodium modified MWNTs(MWNTs-SDBS)on the mechanical and thermal properties of PA66 fibers were comparatively investigated.The results show that compared with the unmodified MWNTs,surface modification of MWNTs can provide homogeneous dispersion and there is a strong interfacial interaction between PA66 and MWNTs-COOH.The tensile strength of nanocomposite fibers reaches a maximum when the mass fraction of MWNTs-SDBS and MWNTs-COOH are 0.1%,which are improved by 27%and 24%,respectively,higher than those of PA66 fibers.Moreover,the incorporation of MWNTs into PA66 improves the crystallizing temperature,crystallinity and thermal stability.A homogeneous dispersion of MWNTs in polymer matrices without agglomeration can be obtained by an easy ball milling and melt spinning method,which can increase the utilization ratio of MWNTs,reduce the amount of MWNTs required,and ultimately improve the mechanical properties at low filler loading.In addition,this method,which is low-cost,easy to operate and does not require the use of solvent,has great potential for industrial application.