Polymethyl methacrylate reinforced with nickel coated multi-walled carbon nanotubes: Flame, electrical and mechanical properties

Composites of polymethyl methacrylate (PMMA) as matrix and nickel-coated multi-walled carbon nanotubes (Ni-MWCNT) as nanofillers were prepared using a melt mixing process. In order to improve the dispersion of the nanofillers in the PMMA matrix and thus enhance matrix-filler interactions, Ni-MWCNT was treated with amino propyl triethoxy-silane (APTS). The shielding effectiveness (SE) of the composites improved with increasing Ni-MWCNT content. In addition, the effects of various combinations of fillers like silver, copper, and nickel nanoparticles on SE have been studied. Among these nanoparticles, copper nanoparticles in combination with MWCNT and Ni-MWCNT showed optimal shielding effectiveness of 55 dB. The volume and surface resistivity of the composites decreased with increase in nanofiller content. The tensile strength values were increased by 51% at 0.8 wt% loading of Ni-MWCNT as compared to that of composite without filler. The improvement in tensile strength was further analyzed using micromechanical models. Cone calorimeter studies showed 25.3% reduction in the peak heat release rate for the composite loaded with 1.5 wt% of Ni-MWCNT as compared to that of neat PMMA. The nanocomposites also showed enhanced thermal stability with the formation of char as the filler content increased.