Mechanical and Electrical Properties of Injection Molded Polymer Matrix Carbon Nanotube Composites

Carbon nanotubes(CNTs)are expected to be one of the most promising nano-materials for improving mechanical properties as well as electrical properties of polymer matrix composites.However，since the size of CNTs is on the nanometer order，there are little reports about the experimental evaluation of their properties by direct manipulation，which is performed in a scanning electron microscope(SEM)，an atomic force microscope(AFM)。In the material design for using nano-materials，it is essential to understand the characteristics of nano-materials experimentally。We attempted to measure Young‘s modulus of various types of CNTs.A cantilever，which is usually used for an AFM and made of silicon，was mounted on the piezo-driving stage。The apparent Young‘s modulus of the CNT is calculated from the conventional relationship between the load applied to the CNT and the displacement of the tip of the CNT。Five types of CNTs are used in the series of experiments.They are ARC-CNTs，CVD-CNTs…More，two types of Vapor-grown CNTs(VGCNTs)；named VG80 and VG50，which are 80 nm and 50 nm in average diameters，respectively。The relative intensities ratio of the D-band around 1350厘米^&lt；-1&gt；to the G-band around 1580厘米^&lt；-1&gt；(ID/IG)in Raman spectra was obtained using the Gaussian fitting.An ARC-CNT was bent like a bending beam by a lateral force applied by a tip of the cantilever.For calculating the apparent Young‘s modulus of CNT，an@equation for the conventional bending beam was applied。Since Young‘s modulus actually calculated includes the influence of the section modulus and indicates the flexural rigidity，it was termed“apparent Young’s modulus”.The apparent Young‘s modulus of the ARC-CNT used here was obtained as 3.3 TPa.This value is slightly lower than the theoretical Young‘s modulus(5.5 TPa)of the single-walled CNT，which was simulated using molecular dynamics.The same measurements and calculation were performed on other CNTs，and the relationship between the apparent Young‘s modulus obtained from TEM measurements and the ID/IG obtained from the Raman spectra is summarized。The result clearly shows that the high-crystallinity CNT has a high apparent Young‘s modulus.Next，we studied injection molding of MWCNT filled polystyrene(PS)and evaluation of the mechanical and electrical properties comparing with the composites in which conventional carbon fillers were filled。As a result，the resistivity of the composites filled with CNT drops significantly between 3 and 4 vol.%and after which it decreases linearly above4vol.%.The resistivity of the composites filled with CNT is 1.2 x 10^2 W·cm when the CNT concentration is 11.6 vol.%。The resistivity is significantly lower than that of the composites which were filled with conventional carbon fillers.The elastic modulus slightly improves with increasing CNT concentration The tensile strength is almost constant in the pristine CNT concentration range from0to12vol.%Then we applied DLC coating and amino-functionalization of CNTs and found that the tensile strength increases up to 20%using the functionalized CNTs in PP matrix.Less：Less

Carbon nanotubes (CNTs) are expected to be one of the most promising nano-materials for improving mechanical properties as well as electrical properties of polymer matrix composites. However, since the size of CNTs is on the nanometer order, there are little reports about the experimental evaluation of their properties by direct manipulation, which is performed in a scanning electron microscope (SEM), an atomic force microscope (AFM). In the material design for using nano-materials, it is essential to understand the characteristics of nano-materials experimentally. We attempted to measure Young's modulus of various types of CNTs. A cantilever, which is usually used for an AFM and made of silicon, was mounted on the piezo-driving stage. The apparent Young's modulus of the CNT is calculated from the conventional relationship between the load applied to the CNT and the displacement of the tip of the CNT. Five types of CNTs are used in the series of experiments. They are ARC-CNTs, CVD-CNTs … More , two types of Vapor-grown CNTs (VGCNTs); named VG80 and VG50, which are 80nm and 50nm in average diameters, respectively. The relative intensities ratio of the D-band around 1350 cm^<-1> to the G-band around 1580 cm^<-1>(ID/IG) in Raman spectra was obtained using the Gaussian fitting. An ARC-CNT was bent like a bending beam by a lateral force applied by a tip of the cantilever. For calculating the apparent Young's modulus of CNT, an equation for the conventional bending beam was applied. Since Young's modulus actually calculated includes the influence of the section modulus and indicates the flexural rigidity, it was termed "apparent Young's modulus". The apparent Young's modulus of the ARC-CNT used here was obtained as 3.3 TPa. This value is slightly lower than the theoretical Young's modulus (5.5 TPa) of the single-walled CNT, which was simulated using molecular dynamics. The same measurements and calculation were performed on other CNTs, and the relationship between the apparent Young's modulus obtained from TEM measurements and the ID/IG obtained from the Raman spectra is summarized. The result clearly shows that the high-crystallinity CNT has a high apparent Young's modulus.Next, we studied injection molding of MWCNT filled polystyrene (PS) and evaluation of the mechanical and electrical properties comparing with the composites in which conventional carbon fillers were filled. As a result, the resistivity of the composites filled with CNT drops significantly between 3 and 4 vol.% and after which it decreases linearly above 4 vol.%. The resistivity of the composites filled with CNT is 1.2x10^2 W・cm when the CNT concentration is 11.6 vol.%. The resistivity is significantly lower than that of the composites which were filled with conventional carbon fillers. The elastic modulus slightly improves with increasing CNT concentration The tensile strength is almost constant in the pristine CNT concentration range from 0 to 12 vol.%. Then we applied DLC coating and amino-functionalization of CNTs and found that the tensile strength increases up to 20% using the functionalized CNTs in PP matrix. Less