| Waterborne polyurethane (WPU) represents a major trend of polyurethane (PU) development and is expected to substitute the solvent based PU because of the increasing concerns about environmental pollution, health and safety risks. WPU have been found in wide applications in many fields such as coatings, adhesives and textiles due to their excellent properties. However, some properties of WPU are inferior to the solvent based PU. Firstly, WPU exhibits weak water resistance in the moisture environment due to the hydrophilic ionic bonds. Secondly, the solvent resistance and mechanical properties of WPU are poor because of its linear structure. The two reasons restrict its further application. UV technology has been developed fast in recent years for its"5E"characteristics (Efficient, Energy-saving, Environmental-friendly, Economical and Enabling). The UV curd resins exhibit high hardness, high solvent and water resistance and good mechanical properties due to its high crosslink density. UV curable polyurethane dispersion (UV-PUD) combines the advantages of both WPU and UV curing systems, such as environmental friendly, fast curable speed, energy saving, excellent performance of films, etc. The conventional UV-PUD is prepared by using a single hydroxyl acrylate (such as 2-hydroxylacrylate) to terminate the polyurethane prepolymer. Therefore, the obtained resins couldn't possess both high C=C content and high molecular weight at the same time which result in defects of the cured films. In order to solve this problems, acrylic diols were synthesized to incorporate into PU chains. The corresponding UV cured films exhibited good properties. But the synthetic process of acrylic diol is somewhat complicated and the reaction condition is very harsh, which have greatly limited its further application.In this dissertation, a novel diol, 2-(3-(((2,2-bis(hydroxymethyl)butoxy) carbonylamino)methyl)-3,5,5-trimethylcyclohexylcarbamoyloxy)ethyl acrylate (BTEA), was synthesized by a facile reaction of the half adduct of isophorone diisocyanate and 2-hydroxyethyl acrylate with trimethylol propane. The new diol was incorporated into the PU side chains in different ratios to obtain UV-PUD. The particle size and viscosity of the emulsion were studied. And the photopolymerization behavior of the films was investigated. Moreover, the effects of BTEA content on the mechanical properties, pendulum hardness, water resistance, MEK resistance and chemical resistance of the UV cured films were also investigated.1. A novel acrylic diol was synthesized by a facile urethane reaction. The structure of the diol was confirmed by Fourier Transform Infrared spectroscopy (FTIR) and Hydrogen Nuclear Magnetic Resonance (1H-NMR). The effects of catalyst, reaction temperature, reaction time and the reactant molar ratio were investigated.2. A series of UV curable waterborne PU dispersion were synthesized by using BTEA as a chain extender. The UV curable acrylate C=C bond was introduced into the side chains by this method, and the C=C content can be controlled by regulating the BTEA /BDO mole ratio. The effect of BTEA content on the emulsion properties was investigated. The photopolymerization behavior of the films was investigated. The mechanical properties, pendulum hardness, water resistance, MEK resistance and chemical resistance of the UV cured films were also studied, respectively.3. Two UV curable waterborne polyurethane dispersions with the same C=C content were prepared by using the synthesized diol (BTEA) and another acrylic diol (TMPME). The particle size and viscosity of the both emulsion was investigated. And the effect of the structure of diol on photopolymerization kinetics was studied. Moreover, the MEK resistance, chemical resistance and mechanical properties of the cured films were compared. |
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