Plastics are indispensable in modern society, but they have inherent weaknesses in mechanical strength, electrical conductivity and thermal conductivity. CNTs have excellent mechanical, electrical and thermal properties, so they are ideal for enhancing the overall performance of plastics. However, traditional technologies cannot uniformly disperse and blend high-load CNTs into polymer matrices. This limits the performance improvement of plastics and severely restricts their advanced applications in cutting-edge materials and devices.
In-situ preparation strategy to solve high-loading compounding challenges
To solve the problem of high-loading compounding, the research team developed a universal compounding technology. This technology combines high-loading CNT networks with thermoplastic polymers to make CNT superplastics. First, they grew continuous CNT networks through floating catalyst chemical vapor deposition. Then, they in-situ continuously impregnated and compounded these networks into various polymer solutions, including polyamide 6 (PA6), polyvinylpyrrolidone (PVP), polyacrylonitrile (PAN), polycarbonate (PC) and polyetherketoneketone (PEKK). This method successfully integrates up to 59 wt% of CNTs, making the CNTs fuse spontaneously with polymer molecules while keeping the original long structure of CNTs. After that, a hot working process further improves the alignment and packing density of the CNTs.
Performance of CNT Superplastics Enabled by Uniform Nanoscale Compounding
The uniform nanoscale compounding of high-loading CNTs greatly improves the material’s overall performance. Drawing on the principle of fishing nets, the research team shrank and densified loose CNT network assemblies in polymer solutions. This allowed high-loading CNTs and polymers to fully contact and compound uniformly at the nanoscale. The highly conductive (electrically and thermally) CNT network gave the plastic excellent mechanical, electrical and thermal properties.
The PA6-based CNT superplastic has a tensile strength of 663 MPa, much higher than that of ordinary engineering plastics, and it also has good resistance to stress relaxation. In terms of electrical conductivity, it reaches 8.6×10 4 S·m –1 , and its conductivity decreases by less than 10% after 100,000 bending cycles. For thermal conductivity, it reaches 143 W·m –1 ·K –1 , which is higher than 304 stainless steel and some aluminum alloys, and hundreds of times higher than typical plastics (about 0.1 W·m –1 ·K –1 ). At the same time, its thermal conductivity anisotropy ratio is about 123, which enables directional heat transfer and gives the CNT superplastic broad application prospects.
Thermoplastic Processability and 3D Printability of CNT Superplastics
The CNT superplastic keeps the excellent thermoplastic processability of ordinary plastics. It can also be made into various complex structures through 3D printing and hot pressing to meet the needs of different application scenarios. For example, the research team made a CNT superplastic heat sink by 3D printing. This heat sink can quickly dissipate heat from a 90°C heat source and achieve excellent directional heat dissipation. Compared with traditional plastics, the superplastic has greatly improved its electrical and thermal conductivity, providing a new way for the development of thermoplastic polymer materials.
National Science Review
Experimental study