While organomodified clays are property enhancing additives for composite materials, much of the research thereof has focused on intercalated quaternary ammonium compounds; however, herein the effects of covalently bound organomodified clays (CoBOCs) are explored with particular emphasis on CoBOC photoinitiators. Two commercially available alcoholic photoinitiators (1hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenylpropanone) were reacted with isophorone diisocyanate to form half-adducts and then reacted with Cloisite 93A, an organophilic montmorillonite clay, to form two CoBOC photoinitiators. The CoBOC photoinitiators were integrated into a standard formulation and subsequently ultraviolet (UV) cured. Property characterization thereof (e.g., adhesion, hardness, and flexibility) yielded unchanged or increased properties with the exception of impact flexibility. Finally, the CoBOC photoinitiators were kinetically characterized via photo-differential scanning calorimetry (photo-DSC) within 1,6-hexanediol diacrylate (HDODA). While increasing concentrations of clay additives generally decrease polymerization rates, increasing concentrations of the CoBOC photoinitiators exhibited increased polymerization rates. Therefore, the CoBOC photoinitiators can enhance the polymerization kinetics and physical properties of UV-curable coatings.
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