Use of supercritical CO₂ as a dispersing agent in the preparation of a polymer‐layered silicate nanocomposite

The usefulness of supercritical CO₂ (scCO₂) in the processing of thermoplastic olefin (TPO) nanocomposites was investigated using a simple extensional flow mixing device. An organoclay (Cloisite^® 20A), a maleated polypropylene (Polybond^® 3200), and a TPO polymer were selected for this study. The three components were combined in different manners to evaluate how scCO₂ influenced the microstructure of a final nanocomposite prepared by different mixing orders of the formulation components. The organoclay was examined in its as‐supplied state as well as after being conditioned under scCO₂. Analyses of the nanocomposites by X‐ray diffraction, transmission electron microscopy, and parallel plate rheology techniques showed that inclusion of scCO₂ during melt compounding significantly contributed to disrupting the crystalline order in the structure of the original organoclay. However, the order by which the formulation components are combined under scCO₂ was important to clay dispersion. It was shown that making use of the proper combination order led to an improvement in the modulus of the resulting nanocomposites as measured by rheology. POLYM. COMPOS., 38:987–995, 2017. © 2015 Society of Plastics Engineers