Reinforcement of Polyamide 6 with Nanoparticles

Polyamide 6 has been reinforced by in situ polymerization of ε-caprolactam by using either 2 wt % of multiwall carbon nanotubes of two different diameters and length or 2 wt % functionalized nonporous Stöber silica. The carbon nanotubes were synthesized by catalytic chemical vapor deposition of ethylene over two different supports: iron particles supported on MCM41 mesoporous silica and iron-cobalt particles on CaCO₃, in order to produce multiwall carbon nanotubes with average diameter of 32 and 58 nm respectively. The Stöber silica particles with diameters of 85 nm and 150 nm were functionalized with 3-aminotrimethoxypropyl silane. The thermal stability of nanotubes/Polyamide 6 nanocomposites increases compared to the neat polyamide 6, and this increase is even larger when the functionalized silica nanoparticles are used as a filler. The crystallinity of polyamide is enhanced when carbon nanotubes are functionalized, but it decreases with or without functionalization of the silica particles. The nanotubes increase the temperature of crystallization in the nanocomposites due to the reduction in the mobility of polymer chains.