Isocyanate functionalization of nano-boehmite for the synthesis of polyurethane organic-inorganic hybrid materials

Eroğlu, Gülden
In this study, organic-inorganic hybrid materials were prepared from polyurethane and boehmite. It was achieved by polymerizing monomers in the presence of functional nano-particles of boehmite with cyanate groups. The produced polyurethane organic-inorganic hybrid materials with enhanced mechanical properties were used for coating applications. Plate-like boehmite nano-particles were produced by hydrothermal process from aluminum hydroxide which was first ground in a high energy ball-mill, and then, processed hydrothermally under pressure and high temperature in a reactor. The surface morphology and crystal structure of boehmite were investigated by Scanning Electron Microscopy and X-Ray Diffraction analyses, respectively. The molecular structures of boehmite particles were investigated by Fourier Transform infrared spectroscopy. Furthermore, Brunauer-Emmett-Teller analysis and Photon Correlation Spectroscopy analysis were carried out to determine the surface area and the size of particles. Then, plate-like boehmite nano-particles were functionalized by the reaction of their hydroxyl groups with 1,6-hexamethylene diisocyanate and 4,4’-methylene diphenyl diisocyanate. Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Differential Thermal Analysis-Thermal Gravimetric Analysis, and elemental analysis were performed for both functionalized and non-functionalized particles to confirm the functionalization of the particles. The polyester polyol used in the production of polyurethane was synthesized from 1,4-butanediol and adipic acid (PE-PO-1), and phthalic anhydride (PE-PO-2). Molecular structure of the polyester polyols was confirmed by Fourier Transform Infrared Spectroscopy analysis and molecular weight of the polymers were determined by end group analysis. Then, the produced functionalized nano-particles and polyester polyols were used for producing polyurethane organic-inorganic hybrid materials. Furthermore, polyurethane polymer and polymer-nonfunctionalized boehmite organic-inorganic hybrids were also synthesized for property comparison. Hardness, impact resistance, scratch resistance, abrasion resistance, and gloss property of the samples were determined. It was observed that mechanical properties of organic-inorganic hybrid materials improved significantly. The hardness of the PU produced with PE-PO-1 increased from 82 to 98 Persoz, and the hardness of the PU produced with PE-PO-2 increased from 52 to 78 Persoz when one weight percentage functionalized boehmite was used. The impact resistance of the coatings was found to depend on the type of the polyols used in PU but not in the inorganic component. Therefore PE-PO-2 used PU has higher impact resistance than PE-PO-1 used PU. Scratch resistance of the coatings improved from 2B to 2H when using functionalized boehmite. Abrasion resistance of PUs produced with PE-PO-1 increased from 2 to 10 l/micrometer and abrasion resistance of PUs produced with PE-PO-2 increased from 12 to 20 l/micrometer by addition of functionalized boehmite.


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Citation Formats
G. Eroğlu, “Isocyanate functionalization of nano-boehmite for the synthesis of polyurethane organic-inorganic hybrid materials,” M.S. - Master of Science, Middle East Technical University, 2011.