Toughness enhancements in poly(methyl methacrylate) by addition of oriented multiwall carbon nanotubes

Abstract

The mechanical properties of multiwall carbon nanotube (MWNT)/poly(methyl methacrylate) (PMMA) nanocomposites were studied as a function of nanotube orientation, length, concentration, and type. Orientation and dispersion were assessed by electron microscopy. A processing parameter study revealed the robust nature of fabricating nanotube/PMMA nanocomposites. An optimal set of extrusion conditions was found for minimizing the aggregate size in single-wall carbon nanotube (SWNT)/ PMMA nanocomposites; this set was also used for the fabrication of the MWNT/PMMA composites. Good dispersion was achieved for MWNTs in PMMA at 0.1-10 wt % loading levels (with the best dispersions at the lower loading levels). The orientation of MWNTs in PMMA proved to be the only way to substantially toughen the nanocomposite. A level of 1 wt % MWNTs in PMMA (oriented nanocomposite) exhibited the largest increase in tensile toughness with a 170% improvement over oriented PMMA. Increases in the modulus and yield strength were not nearly as pronounced (and occurred only at the highest loading of MWNTs, which was 10 wt %) with increases of 38 and 25%, respectively. A failure mechanism was proposed in which orientation of the MWNTs (normal to the direction of craze propagation and crack development) enabled them to toughen the brittle PMMA by bridging cracks that developed (via craze precursors) during the tensile test. None of the nanotube/PMMA composites showed mechanical properties close to the values expected from simple rule of mixture and orientation considerations.

Influence of Processing on Morphology, Electrical Conductivity and Flexural Properties of Exfoliated Graphite Nanoplatelets-Polyamide Nanocomposites

“…These results suggest that the dispersion of xGnP in CNR processed PA6 nanocomposite is better than that in CoR and MCoR processed nanocomposites. This is consistent with the results Gorga [17] reported.…”

Microinjection Molding of Enhanced Thermoplastics

“…However, for weight percentages higher than 7% the mechanical properties of the PMMA/CNT composite starts to decrease and for 10 wt% the composite becomes brittle. Later, Gorga & Cohen (2004) presented results consistent with the previous one. They studied the mechanical properties of MWCNT/PMMA as a function of nanotube orientation, length, concentration and type.…”

“…Different polymeric matrices have been considered, such as PMMA (Jia et al, 1999;Gorga & Cohen, 2004), polystyrene (PS) (Qian et al, 2000;Yang et al, 2005), polypropylene (PP) (Dondero & Gorga, 2006;Bao & Tjong, 2008), polyurethanes (PU) (Koerner et al, 2005;Xiong et al, 2006;Zhang et al, 2011) and polyethylene (PE; high density polyethylene -HDPE, ultrahigh molecular weight polyethylene -UHMWPE) (Ruan et al, 2003;McNally et al, 2005;Kanagaraj et al, 2007;Fonseca et al, 2011). …”

Utilization of poly(methyl methacrylate) – carbon nanotube and polystyrene – carbon nanotube in situ polymerized composites as masterbatches for melt mixing

“…Well-aligned CNTs in the composite improve mechanical properties [1,2]. Tensile toughness of poly(methyl methacrylate) (PMMA) increased 170% after addition of 1!wt% CNTs, which were oriented in the matrix [1]. On the other hand, electrical conductivity decreases in well-aligned CNTs [3][4][5].…”

“…The orientation of the CNTs in composites has contradictory effects on the properties of the composite. Well-aligned CNTs in the composite improve mechanical properties [1,2]. Tensile toughness of poly(methyl methacrylate) (PMMA) increased 170% after addition of 1!wt% CNTs, which were oriented in the matrix [1].…”