Thermal expansion properties of the polycaprolactam nanocomposites reinforced with single-walled carbon nanotubes

The effect of carbon nanotube loading and aspect ratio on the thermal expansion properties of polymer nanocomposites was investigated in terms of the material properties, configuration, and phase geometry of each individual component. The objective of this research is to provide methods for fabricating carbon nanotube reinforced polymer nanocomposites with very low coefficients of thermal expansion. The thermal expansion properties of polycaprolactam nanocomposites prepared with different levels of thermal histories were investigated to gain a better understanding of the morphology-property relationships. The effects of carbon nanotube loading and aspect ratio on the thermal expansion behavior of the polymer nanocomposites were evaluated. The results indicated that the loading and aspect ratio of carbon nanotubes have a significant effect on the thermal expansion properties of the polymer nanocomposite, and high aspect ratios and loading of the filler are preferred. The issue of carbon nanotube dispersion is critical to efficient reduction in thermal expansion properties. Additionally, it is desirable to achieve a high degree of alignment of carbon nanotubes in the matrix along the desired direction for fabricating polymer nanocomposites with very low coefficient of linear thermal expansion in this direction. Furthermore, flow-induced alignment of carbon nanotubes in the matrix along the direction of flow leads to reduced thermal expansion properties of the polymer nanocomposite. Finally, there is an excellent linear correlation between the relative Young's modulus and the relative thermal expansion of the nanocomposite and the matrix.