Carbon Nanotube Composites: Properties and Applications

Carbon nanotubes (CNTs) are coaxial hollow tubular nanoscale materials formed by the aggregation of a large number of carbon atoms under certain conditions. Its radial size is on the order of nanometers, and its axial size is on the order of micrometers. It belongs to carbon isotope isomerism. A new member of the family is the ideal one-dimensional quantum material. Since Iijiman discovered CNTs in 1991, its excellent performance has led to extensive research. However, CNTs are insoluble in common organic solvents, and their surface properties are close to that of graphite, making the surface chemically inert, thus limiting its application range. From the current situation reported in the literature, the most effective way to solve these problems is to modify the surface of CNTs, increase their dispersibility and chemical activity. The surface modification method usually adopts the following methods: First, different reactive groups such as carboxyl groups are introduced at the ports or defects of CNTs through different oxidation treatments, and then they are further grafted and modified by esterification or amidation reaction. . Because CNTs have a similar structure to polymers, they can be composited with high-performance composites. Such composite materials have broad application prospects in the fields of electronic devices, wave-absorbing stealth materials, and other structural materials.

CNTs/Polymer Composites Performance (1) Conductivity and Thermal Conductivity CNTs have better electrical conductivity than copper and can be used as a substitute for metal fillers to prepare organic composite conductive materials. Because the compatibility of CNTs with organics is superior to that of metals, the properties of the materials are more stable and the quality is lighter. At the same time, the aspect ratio of up to 10,000 CNTs can greatly reduce the percolation threshold of the composites, which cannot be achieved by other fillers. Can be used as anti-electric material. Adding CNTs can greatly improve the thermal stability of composites.

(2) Mechanical properties The CNTs after acid treatment were composited with high-density polyethylene (HDPE). Directional CNTs/HDPE composites were prepared by mechanical blending. The addition of CNTs increased the yield strength and tensile modulus of the composites. , but at the same time it reduces the breaking strength and elongation at break of the material. Using CNTs to modify phenolic resin (PF), CNTs can significantly improve the bending strength, compressive strength, interlaminar shear strength and impact strength of PF/CF composites.

(3) Tribological properties Polytetrafluoroethylene (PTFE)-based composites were prepared using CNTs as filler. The friction coefficient of CNTs/PTFE composites decreased with the increase of CNTs content, and its wear resistance was significantly better than that of pure PTFE. CNTs are used as fillers to effectively inhibit the wear of PTFE.

(4) Anti-static properties The CNTs were added to polypropylene by the method of blending and spinning, and their anti-static properties were studied by measuring their frictional electrostatic charge. The results show that it is difficult to increase the antistatic performance of polypropylene (PP) fibers by adding a small amount of CNTs alone, and adding antistatic agents containing carbon nanotubes can effectively improve the antistatic properties of PP fibers.

(5) Flame Retardant Performance The two new flame retardants SPS and PTE were compounded with ammonium polyphosphate (APP) and MWNTs, and applied to low density polyethylene (LDPE) to obtain intumescent flame retardant LDPE-MWNTs composite. material. In the intumescent flame retardant system, there is a significant synergistic flame retardant effect between the IFR and MWNTs, and the flammability and heat release rate (HRR) of the low density polyethylene is greatly reduced, and the amount of residual carbon after combustion is greatly increased. increase.

Applications of CNTs/Polymer Composites CNTs have great potential as reinforcement and conductive phases in the field of nanocomposites. Among them, the application of CNTs/polymer composites has developed the fastest. When the CNTs are used as the conductive medium of the conductive paint, the smaller the diameter of the CNTs, the better the conductive coating obtained is. The optimal aspect ratio of CNTs as the conductive medium for conductive coatings is approximately 250. When the aspect ratio of CNTs is greater than 250, the electrical conductivity of the prepared coating decreases with the aspect ratio increasing. When the aspect ratio of CNTs is less than 250, the electrical conductivity of the prepared coating increases with the aspect ratio. And increase. In general, the higher the content of CNTs, the better the electrical conductivity of the resulting coating. For the new generation of stealth stealth materials, it requires strong absorption, wide frequency band, light weight, thin thickness, multi-function, infrared microwave absorption compatibility and excellent other comprehensive performance requirements, utilizing the special electromagnetic absorption characteristics of CNTs, and polymers Excellent material properties, research and development of CNTs polymer-based composite wave-absorbing functional materials is an effective way to achieve this technology.