A di-or triaziridinyl compound served as the latent curing agent for the prepared carboxylic groups containing aqueous-based polyurethane (PU) dispersions. It was formulated as a single pack self-curable aqueous-based PU system. This system was stable under an alkaline environment and its curing reaction could be initiated by a pH control. A model reaction between a monoaziridinyl compound and formic acid was demonstrated and identified by infrared spectrophotometry. The stabilities of this convenient one-package PU system with a different dosage of di-or triaziridinyl latent curing agent were monitored by a particle sizer and fluorescence spectroscopy. The PU films were cast and self-cured from these single pack PU dispersions at ambient temperature. The physical and mechanical properties as well as thermal behaviors of each self-cured PU were evaluated.

ABSTRACT:The carboxyl group containing aqueous-based polyurethane (PU) dispersions were prepared from isophorone diisocyanate, poly(propylene glycol)-1000, and 2,2-dimethylol propanic acid via a PU prepolymer process. The amino content of this amino-terminated aqueous-based PU system was determined by a styrene oxide titration method. Glycidyl methacrylate (GMA) copolymer emulsions were prepared by an emulsion polymerization of GMA and other alkyl acrylates. The curing behavior of the GMA copolymer was demonstrated by a model reaction of the GMA copolymer with ethylenediamine. In the same token, the reaction took place between the PU amino groups and the GMA copolymer epoxides at ambient temperature and resulted in the formation of a hybridized homogeneous copolymer. This hybridized copolymer also consisted of carboxylic acid on the PU fraction after drying. Carboxylic acids of the copolymer were exchanged with calcium ion and this ionic coordination resulted in a calcium ion-crosslinked copolymer. The physical and mechanical properties and the thermal behaviors of the hybridized copolymers were evaluated.

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Water-reducible acrylate copolymer is obtained from a free-radical copolymerization of n-butyl acrylate, acrylic acid, and methacrylic acid. Self-emulsified aqueous-based polyurethane (PU) anionomer is prepared by the conventional method. The latent curing agents (di-and triaziridinyl compounds, HDDA-AZ and TMPTA-AZ) are synthesized from the reaction of aziridine with hexandiol diacrylate and trimethylolpropane triacrylate, respectively. These two polymers and the latent curing agent are miscible in each other and become a single component and selfcurable polymer dispersion. The carboxyl ions of polymers not only stabilize the aqueous polymer dispersions but also serve the curing site toward latent curing agent in the drying process. These two polymers blend with a curing agent, which results in new polymer hybrid formation. These polymer hybrids have the improvements on performance properties and the cost/performance benefits.