Influence of Silanization Treatment on Thermomechanical Properties of Multiwalled Carbon Nanotubes: Poly(methylmethacrylate) Nanocomposites

Unfunctionalized and silanized multiwalled carbon nanotubes (MWNTs) were incorporated in poly(methylmethacrylate) matrices using in situ polymerization. Polymer-compatible functional groups on carbon nanotube (CNT) surfaces were characterized by infrared spectroscopy. These chemical moieties improve interaction at interfaces, allowing transfer of mechanical load between the matrix and the dispersed phase as reflected in the resulting improved mechanical and thermophysical properties. The composites were characterized by Raman spectroscopy to evaluate molecular level interactions and dynamical mechanical analysis. Composites with silanized CNTs have higher storage modulus (E′) than polymer reinforced with unfunctionalized nanotubes. Considering the average of the samples, only 1 wt.% of silanized nanotubes provides an increase in E′ of 165% at room temperature with respect to polymer matrix, and the increments reached are by a factor of 6.8 and 13.6 over the polymer matrix at 80°C and 90°C, respectively. 1 wt% of silanized CNTs increases the glass transition temperature of polymer matrix around 30°C. Microscratch testing results of composites show that unfunctionalized CNTs cause deeper penetration of the indenter than polymer matrix at the same force; however, the composites developed with silanized CNTs present more regular behavior than polymer reinforced with unfunctionalized CNTs