Shear-induced 1-D alignment of alumina nanoparticles in coatings

Abstract

Atomic Force Microscopy and Scanning Electron Microscopy were used to study shear-induced alignment of alumina and silica nanoparticles in twocomponent polyurethane clear coatings. 1-D strings of nanoparticles, formed in an extended pearl-necklace fashion were observed near the surfaces of cured films at nanoparticle volume fractions less than 0.05. This alignment is affected by the shear conditions of the application method. When applied by spraying, linear particle strings as long as 5 cm were observed in the direction of shear. Nanoparticle strings were also found, to a lesser extent, when coatings were applied by a drawdown method. The phenomenon was not observed in coatings applied with minimal shear. These particle string formations, in addition to affecting the performance of coatings, may have broader implications in the field of nanomaterials. Our literature searches so far have not uncovered reports of stable, 1-D nanoparticle arrangements with same degree of linearity produced under simple shear with compositions having very low particle loadings.

Thermal‐initiated hydroxyethyl methacrylate functionalization of multiwalled carbon nanotubes

“…This suggests nanolevel dispersion within the colloidal structures. The one‐dimensional alignment of nanoparticles via shear has already been demonstrated with alumina and silica nanoparticles,15 but little has shown these effects for CNTs in a two‐component polyurethane coating as reported here.…”

“…The main objective of this study was to separate agglomerated MWCNTs via tip ultrasonication9, 14 in a tetrahydrofuran (THF)/2‐hydroxyethyl methacrylate (HEMA) solution for subsequent SIP of HEMA. The secondary objective was to determine if the one‐dimensional alignment of nanoparticles observed in other studies could be reproduced using poly(HEMA)‐MWCNTs in a two‐component polyurethane coating 15–17. This was achieved by adding the poly(HEMA)‐MWCNTs to a two‐component polyurethane‐coating formulation.…”

Effect of Nanoalumina on the Electrochemical and Mechanical Properties of Waterborne Polyurethane Composite Coatings

“…They can be added to a clear coating formulation with little or no adverse impact on visual characteristics. Nanoparticles most commonly used in coatings are SiO 2 [7,[11][12][13], TiO 2 [16], ZnO [6,8,9,17], Al 2 O 3 [18][19][20][21], Fe 2 O 3 [22], and CaCO 3 [23], ZrO 2 [24]. Use of nanoparticles is most commonly based on the inherent properties they possess.…”

New approach for simultaneous enhancement of anticorrosive and mechanical properties of coatings: Application of water repellent nano CaCO3–PANI emulsion nanocomposite in alkyd resin

“…The improvement in the properties of the nano coatings is attributed to their small size of pigments and fillers [5]. Nanomaterials mostly used in coating system, normally are SiO 2 [3], TiO 2 [6], ZnO [7], Al 2 O 3 [8], Fe 2 O 3 [9] and also some metals like nano-aluminum [10], nanotitanium [11], etc. are also being used for modifying the organic coatings.…”