Thermal stability of nanoclay-based pigments in polypropylene matrix

A nanoclay-based pigment (NCP) by means of intercalating montmorillonite (MMT) with cationic dye methylene blue was prepared and applied for coloring of polypropylene (PP). The methylene blue intercalated MMT pigment were characterized using X-ray diffraction (XRD) and thermogravimetry (TGA/DTG) analysis. The results showed that intercalation of dye molecules within the interlayer spaces of MMT successfully occurred, and an increase of 5.9Å in the basal spacing was achieved. TGA/DTG data showed gradual and slower rate of weight loss during heating for the pigment compared to methylene blue suggesting improved thermal stability of the intercalated dye. After melt mixing of NCP with polypropylene, the heat resistance of colored PP-pigment composites was assessed. Results showed a significant improvement in pigmented PP compared to the PP-dye sample.