Photo-stability of rhodamine-B/montmorillonite nanopigments in polypropylene matrix

A rhodamine-B based nanopigment was developed as a colorant for polypropylene products. The cationic dye rhodamine-B was intercalated into Na+-montmorillonite (Cloisite Na+) in an acidic medium. The dye-intercalated montmorillonite was centrifuged, dried and milled to prepare the nanopigment particles before mixing with polypropylene. X-ray diffraction studies on the intercalates showed an increase in the basal spacing, thus confirming intercalation of the dye molecules within the nanostructures of the interlayer spaces. Thermo-gravimetric investigations suggested improved thermal stability of the intercalated dye. UV-exposure tests on colored polypropylene/nanopigment composites showed a significant improvement in the photo-stability compared to the polypropylene/dye samples.