Reactive Nanofluids for Tuning Resin Hardness
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2018.678
Reactive Nanofluids for Tuning Resin Hardness John Texter,* Zhiming Qiu,§ Joe Byrom,¶ and Rene Crombez School of Engineering and Coatings Research Institute, Eastern Michigan University, Ypsilanti, MI 48197, USA § Present Address: College of Materials Science & Engineering, South China University of Technology, Guangzhou 510640, P.R. China ¶ Present Address: Hentzen Coatings Inc., 6937 W Mill Rd, Milwaukee, WI 53218, USA
ABSTRACT
Polyurea resins derived from tolyldiisocyante (TDI) and a reactive solvent-free nanofluid (NF-NH2) surface-decorated with propylamines can be tuned over three to five orders of magnitude in storage modulus (10 MPa to 10 GPa) and hardness modulus (6 kPa to 4 GPa) by varying weight fractions of components. The thermal properties of this NF-NH2 are similar to several other nanofluids reported using the same bulky anionic counterion that also imparts liquidity in the absence of any solvent. This tuning suggests applications ranging from opaque protective coatings to clearcoats to sealants to adhesives.
INTRODUCTION Solvent-free nanofluids (NFs) that are supramolecular ionic liquids were introduced by Leone and co-workers in 2001 as a molten form of DNA [1] and by Bourlinos and coworkers from Cornell in 2004 and 2005 as viscous nanoparticle liquids [2-5]. These supramolecular ionic liquids typically are composed of a core and a corona, wherein the corona typically emanate from surface-modifying ionic liquid salts. Ionic liquid counterions often are referred to as “caps.” A zoology of such liquids now includes 0D, 1D, 2D, and 3D cores such as metal nanoparticles, carbon allotropes, proteins, viruses, and many metal oxides [6]. Physical chemical functionality introduced by corona induces classical liquidity and flow in an absence of added molecular solvent. A different class of NFs comprising alkyl and aryl derivatives of fullerenes comprising only one to several surface modifying groups has been examined by Nakanishi and co-workers [7,8]. An example in this class having epoxy-functionalized
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corona substituents was subjected to cationic photopolymerization by Lintinen and coworkers to make polymeric thin films [9]. Supramolecular ionic liquid-based NFs are obtained by including a minor but reactive surface component and define a subclass of NFs. Such NFs and their application were introduced in 2009 [10,11]. Archer and co-workers followed with an application formulating polyurethanes [12]. UV free-radical photopolymerized acrylate NFs [13,14] and isothiocyanate NFs [15] have also been reported and used to produce new classes of resins and clearcoats. Amine surface functionalization was followed by converting these functionalities to isothiocyanates with thiophosgene. These nanof
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