Polyurethane/Clay Nanocomposite Coatings with Organoclay Modified by Organifier Having Multiple Cationic Sites

Abstract

In this dissertation, organifiers having multiple cationic sites with various molecular weights are synthesized and organoclays are prepared by cation-exchange reaction of montmorillonite with organifiers. Molecular weight of organifiers is varied from 4455.54 to 10326.73 and one, two and four cationic sites of organifiers are prepared. NMR and FT-IR measurements are used to verify the synthesis of organifiers. By the TGA analysis, inorganic contents of organifiers are measured. d-spacing of organoclays are estimated by WAXD and SAXS analysis. SEM is used to observe the size of organoclays and average effective size is calculated by image analysis. 2K-H-2K organoclay showed the largest d-spacing and the best thermal stability and the most amount of organic penetration into clay among prepared organoclays. Prepared organoclays are immersed into DMF and sonication is applied for 10 mins. After the sonication, organoclay is well-dispered and form stable suspension in DMF. Polyurethane/organoclay nanocomposites are synthesized via solution polymerization. With the five kinds of prepared organoclays, polyurethane/organoclay nanocomposites are prepared from 1 wt% up to 3 wt% organoclay loading. Polyurethane/organoclay nanocomposites are characterized by rheometer, TGA, DMTA, WAXD, SAXS, SEM, TEM, GPC, and UTM. Agglomerated residual clays are observed by SEM micrographs and TGA is used to evaluate thermal stability. Organifier of organoclay is extended by reaction with isocyanate through solution polymerization and the increase of molecular weight is estimated by GPC. Enhancement of mechanical properties and glass transition temperature are observed by UTM and DMTA, respectively. Physical crosslinking effect by ions is verified by rheometer measurement and observed by TEM analysis. The greatest properties are observed from polyurethane/2K-H-2K organoclay nanocomposite corresponding to results of organoclay. Ionic crosslinking effect is shown by introducing multi...