Morphology and tensile properties of PMMA carbon nanotubes nanocomposites and nanocomposites foams

Poly (methyl methacrylate) (PMMA) and multi-walled carbon nanotubes (MWCNTs) nanocomposites were synthesized and foamed by supercritical carbon dioxide. Morphology and tensile properties of both solid and foamed nanocomposites were investigated. Moderate improvement in the tensile properties was observed in the solid nanocomposites, which depended on carbon nanotube (CNT) dispersion and polymer–CNT interaction. The CNTs had significant influences on the foam cell morphology. Moreover, the convoluted effects of CNT dispersion, polymer–CNT interaction and foam structure differences led to significant difference in foam properties. Nanocomposite foam with concurrent increases in tensile strength (∼40%), tensile modulus (∼60%) and strain at break (∼70%) was successfully prepared with the use of 0.5% functionalized CNTs that were well dispersed. The foam showed a ductile failure under tension that involved extensive pore deformation and collapsing, and formation and coalescence of microvoids that were largely responsible for the significantly improved tensile toughness. By contrast, foam properties were reduced in the presence of poorly dispersed CNTs that weakly adhered to the matrix.