Abstract:
Bright red pigments, based on montmorillonite (MM) intercalated with rhodamine 6G (R6G) have been developed for the purpose of pigmenting polyethylene-based polymers. The cationic dye R6G was intercalated into NH(4)+-saturated MM in a slightly acidic medium. The resultant inorganic-organic MM complex was characterized using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared (FTIR) spectra, diffused reflectance, and color measurements. Expansion in basal spacing from an initial 11.3 to similar to 15.8 A was detected in the X-ray profile, confirming clay intercalation with R6G. The average particle size of the intercalated clay was 35 nm as measured by photon scattering. Frequency shifts of the C-H bending vibration from 724 to 744 cm-1 and that of the carbonyl (> C=O) stretching vibration from 1647 to 1666 cm-1 have been observed as a result of intercalation in FTIR spectra. Improvement in thermal stability for the intercalated MM was indicated by results from thermal analysis. The intercalated colored polyethylene-pigment showed enhanced stability under exposure to ultraviolet radiation of wavelength of 200-400 nm. The values for color coordinates were a*=53.45 and b*=9.62 from the color measurements.
