Description:

Composite materials composed of polymers blended with reinforcing fillers play a major role in various technologies. An important example, commercial rubber, incorporates carbon black fillers, which significantly enhance mechanical properties such as Young’s modulus and ultimate strength. The carbon black fillers consist of nanoparticle chain aggregates (NCAs). Because the mechanisms behind the filler effects are poorly understood, researchers have studied the dynamics of NCAs composed of carbon particles synthesized by laser ablation. In situ stretching of the NCA was carried out in a transmission electron microscope (TEM), first in the absence of a supporting polymer matrix and then embedded in a polymer film. For an isolated NCA, after initial reorientation and unfolding of the chain, a large strain led to its elongation, plastic deformation, and breakage, followed by fast recoil of the broken segments. On the other hand, a small strain could be partially recovered by subsequent contraction, displaying elastic behavior.  Finally,  commercial carbon black fillersembedded in a poly(acrylic acid) polymer film also demonstrated stretching andreorientation similar to those of the NCA-polymer films. The results point to a possible mechanism of enhanced mechanical properties of carbon black nanocomposites: namely, separate contribution to the overall properties by the stretching and elastic properties of filler materials embedded in the polymer matrix.

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