Macroscopic Inspection for Nanofiller Dispersion and Polymer Degradation: Fundamental Characterization in Polymer Nanocomposites

Polymer-based nanocomposites involving various organic and inorganic nanofillers continue to be of great scientific and commercial interest. The common challenge is the fabrication of effective nanocomposites with well-dispersed and well-separated (exfoliated) filler morphology, and there have been different fabrication methods reported in the literature, ranging from solution to melt and solid-state processing.

One fundamental characterization that is often overlooked in polymer nanocomposites is simply of the physical appearance of the resulting specimens; macroscopic inspection of the fabricated nanocomposites is often ignored or left undiscussed in the literature. Considering that many of these materials are designed for real-world applications in consumer products and packaging, this is rather surprising.

In this paper, post-fabrication, physical appearance characterization of polymer-based nanocomposites is conducted. A series of specimens of prototypical nanocomposites are considered, including base polymers like polypropylene, polystyrene and poly(lactic acid), and nanofillers such as organically-modified clay, graphite and carbon nanotubes. The effects of different fabrication methods and post-production processing methods are evaluated.

In melt-mixed nanocomposites, organically-modified nanofillers have the highest tendency to degrade the base polymer, resulting in non-uniform, dark brown color unsuitable for packaging applications. Low-temperature, solid-state processing can suppress the degradation and discoloration of the polymer nanocomposites to some extent. Carbon-based nanofillers such as carbon black, graphite and carbon nanotubes, when properly processed, lead to uniformly black specimens, which can be suitable for certain commercial applications.