Effect Of Adding Amino-Modified Carbon Nanotubes On The Pore Structure Of Polyurethane Foams

Polyurethane materials, with excellent physical and chemical properties, are widely used in automobile manufacturing, energy conservation, high-performance adhesives, new environment-friendly coatings and so on. Among them, polyurethane foams (PUFs) are one of the most important members. PUFs not only have low density, aging resistance, chemical resistance and excellent thermal insulation, but also has high production efficiency and low cost, so they are widely used as insulation materials, such as in refrigerator manufacturing, construction materials and some oil pipelines. However, the PUFs materials currently used are difficult to achieve some special requirements for their low mechanical properties. Therefore, it is urgent to improve the physical properties of PUFs for more applications.In this paper, we prepare some reinforced PUFs by adding modified carbon nanotubes (CNTs) to the system, and discuss the effects of pore-structures and mechanical properties of PUFs made by several factors such as isocyanate index, polyols proportion and foam agent content. The results show that, with the increase in the isocyanate index, the pore size of PUFs decrease in the beginning and then increase; As the contents of glycerol decreases, the pore size of PUFs increase, a clear polygonal pore structure is gradually formed, finally the stable triangular frame structure between the cell appears; Furthermore, with the increase in foam agent content, the pore size of PUFs increase, and the pore walls become thinner.Because of large specific surface area and the strong interaction, it is easy to agglomerate for CNTs. In order to improve their dispersion in the polyurethane matrix, the surface modification of CNTs by chemical modification method is used. Firstly, we introduce some functional groups such as hydroxyl and carboxyl on the surface of CNTs by acid oxidation methods, and then amino compounds are grafted to the surface by esterification and amidation reaction, so as to obtain amino functionalized CNTs. There is no obvious agglomeration happened in the PUFs filled with modified CNTs, and the cellular structure and mechanical properties of PUFs both improve. The results of compressive strength and modulus of PUFs with different types of fillers show that PUFs-MWCNTs-NH2> PUFs-MWCNTs-OH> PUFs-MWCNTs>PUFs. With the increase in content of MWCNTs-NH2, the compressive strength of samples increased in the beginning and then decreased, with a maximum compressive strength of 0.14MPa when added to 0.75% MWCNTs-NH2, which is respectively increased by 75% and 100% compared with the PUFs with 0.25% and 0% MWCNTs-NH2.