UV Curable Polymers with Organically Modified Clay as the Nanoreinforcements
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L11.45.1
UV Curable Polymers with Organically Modified Clay as the Nanoreinforcements Fawn M. Uhla,*, Brian R. Hinderliterb, Siva Prashanth Davuluric, Stuart G. Crollb, Shing-Chung Wongc, and Dean C. Websterb,* a
Center for Nanoscale Science and Engineering Department of Polymers and Coatings c Department of Mechanical Engineering and Applied Mechanics North Dakota State University, P.O. Box 5376, Fargo, ND 58105 b
ABSTRACT UV curable polymers are prevalent in microelectronic applications. Several advantages are associated with UV curing such as rapid cure, solvent free systems, application versatility, low energy requirements, and low temperature operation. To be used in electronics the films must posses the following attributes: high glass transition, barrier properties, low shrinkage, flexibility, and enhanced mechanical properties. The area of polymer-clay nanocomposites have been widely investigated by researchers and improved mechanical, thermal, and barrier properties were reported. Most researchers have attempted nanocomposite formation by melt mixing or in situ polymerization. Little is understood on UV curable nanocomposites. This paper seeks to examine nanoclay-containing polymers using organomodified montmorillonites in UV curable systems and the effects of such clay inclusions on the properties of UV cured films. By x-ray diffraction it appeared that intercalated structures were formed. In the case of an epoxy acrylate formulation an increase in glass transition temperature was observed for formulations containing clay. INTRODUCTION Various research groups have shown an interest in clay-polymer nanocomposites. Claypolymer nanocomposites have shown improved mechanical properties, barrier properties, thermal stability, and chemical resistance at low loadings of clay.[1-4] UV curable films are increasingly being used in micro- and consumer electronics industries due to their rapid cure, solvent free characteristics, application versatility, low energy requirements, and low temperature operation.[5, 6] Final application of the film determines requirements necessary for use, but some properties being sought are: fast cure, transparency, flexibility, dimensional stability, chemical resistance, thermal stability and good adhesion. Preparation of clay nanocomposites has typically been done thermally either by in situ polymerization or melt blending, and improved properties have been reported. Decker et al. prepared a UV curable system containing clay and showed by XRD that an exfoliated structure exists.[7] The effect of nanoreinforcement on properties has not been examined for these systems. Based on the properties achieved with clay-polymer nanocomposites it is advantageous to examine UV curable clay-polymer films to determine the effect on properties.
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EXPERIMENTAL Materials Nanomer clay was obtained from Nanocor. CN121, a low viscosity epoxy acrylate, and SR454, an ethoxylated (3) trimethylolpropane triacrylate, were obtained from Sartomer. The photoinitiator Darocur 1173, 2-hydroxy-2-methyl-1
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