Preparation of clay-dye pigment and its dispersion in polymers

摘要

This thesis is concerned with an experimental study of clay intercalation by organic dye molecule which is crucial for the successful development of a stable clay-dye pigment with combined advantages of organic dye and inorganic clay. Clay-dye pigments were prepared by two different methods. Two different organic dyes were used with unmodified clay and modified clay to study the intercalation. Characteristics of clay-dye pigment have been investigated using X-Ray Diffraction, Thermo-gravimetric Analysis and Transmission Electron Microscopy. In this thesis it is shown that the absorption of cationic dye by unmodified clay in aqueous medium mainly takes place in the interlayer clay surface. More likely the dye molecules with aromatic quaternary ammonium cation intercalate the clay layer and strongly interacts with the clay interlayer oxygen plane, where solvent dye (which is hydrophobic in nature) adsorption by unmodified clay mainly takes place on outer surface of the clay. Dye molecules are weakly interacted with outer surface oxygen plane by hydrogen bonding or Vander Waals forces. Modified clay enabled the solvent dye to intercalate inside the clay interlayer surface with the suitable non-aqueous medium (because of its expanded structure). The modified clay suspension in the selected non-aqueous medium shows only partial desorption of alkyl ammonium molecule from the clay layer with the presence of both cationic dye and solvent dye. Therefore the penetrated dye molecules must have weakly interacted with the interlayer oxygen plane as well as the remaining alkyl ammonium molecule present inside the clay layer. It is believed that the thermal and UV stability of organic dye can only be facilitated by a specific interaction (Ĉ-interactions) between aromatic alkyl ammonium cation of organic dye molecule and the interlayer oxygen plane of clay minerals. This interaction possibly enables the high thermal energy or the energy of the UV radiation to transmit immediately into the clay layer. Therefore organic dye molecules are protected from high energy loading and hence thermal and UV stability are improved.