9A) study on the effect of multi-arm, multi-site organifier on the properties of polyurethane/clay nanocomposite coatings

Abstract

Linear one or two binding sites, three-arm, one binding site and three-arm, three binding sites $(N^+)$ organifiers with two hydroxyl end groups were synthesized. The novel organoclays were prepared through cation exchange reaction between pristine montmorillonite (Na-MMT) and the synthesized organifiers. The effect of the chemical structure and the molecular weight of the organifiers on the properties of the organoclays such as d-spacing and suspension stability in organic solvent were investigated. The effect of different organoclays on the properties of the PU/clay nanocomposites such as morphology, molecular weight, thermal properties, tensile properties and rheological properties was also investigated. In chapter 2, the effect of the chemical structure and the molecular weight of the organifiers on the properties of organoclays were investigated. Higher ion-exchanged fraction (IEF) was observed for one binding site organoclays when compared to the multi binding site organolcays because the one binding sited organifier is easier to penetrate into the silicate layers than multi binding site organifier and/or there is some possibility of just one or two $N^+$ in multi binding sited organifier was attached to the anion of the layered silicate surface. The d-spacing of organoclays increased with increasing the molecular weight of organifiers at the same series due to the increase of its chain length and the formation coil-like structure between the silicate layers. The average sizes of Cloisite 30B and Cloisite Na+ are about 9um while the average sizes of the organoclays are rather big ranging form 67-114um because the clays are surrounded by the sticky organifiers. However, the average sizes of organoclays are reduced to about 1um after sonication in DMF for 10min. Cloisite 30B and Cloisite Na+ could not form the stable suspension in DMF due to the lack of the interaction with DMF while orgaonclays showed suspension stability in DMF because the organifiers a...