Design, synthesis, and study of novel fluoro-urethane monomers for emulsion polymers and study of oxygen-scavengers for ultraviolet curable powder coatings
The research focused on two areas of environmentally friendly coatings: waterborne and powder coatings. Emulsions containing fluorinated species present a variety of unique and desirable properties; however, incorporation of these monomers can be problematic which stems from the inherit hydrophobic nature of the -CF 2 - and -CF 3 groups. In this research, fluorinated alcohols were reacted with difunctional isocyanates followed by methacrylated alcohols to produce fluorinated urethane monomers. The conversion was monitored using Fourier transform infrared spectroscopy (FT-IR) while the final conversion was established using gel permeation chromatography (GPC). The structure was confirmed using 1 H and 13 C nuclear magnetic resonance (NMR), and the hydrophobicity of these monomers was determined via high performance liquid chromatography (HPLC) with a dimethylformamide mobile phase. The fluorinated urethane monomers exhibited a decreased hydrophobicity as compared to the directly methacrylated analogs. Upon emulsion polymerization in a standard acrylic formulation, the fluorinated urethane monomers did not require special procedures or additives as do most directly (meth)acrylated monomers. The latexes exhibited similar properties to other fluorinated latexes such as high water contact angle. Ultraviolet (UV) curable powder coatings are increasing in popularity due to their numerous advantages. One of their limitations, however, is their vulnerability to oxygen inhibition. An inexpensive, practical solution still eludes research into the problem of oxygen inhibition. Phosphines, phosphites, and similar triaryl Group 15 analogs were incorporated in to UV curable powder coatings (UVPCs) to alleviate this problem. The masterbatch method proved successful in synthesizing UVPCs. After solvent removal, each UVPC masterbatch was ground and sized to <120 >μm. The rate of polymerization of the UVPCs was then determined using the photo-differential scanning calorimeter (photo-DSC) at 120°C. Triphenyl phosphine (TPP) incorporated at one weight percent (1%) increased the UVPCs rate of polymerization in air to nearly that of the same powder coating in an inert atmosphere while eliminating the oxygen induction period with only 1% of photoinitiator. The phosphites and triaryl Group 15 analogs proved effective but not to the extent of TPP. Common powder coatings additives like flow agents and degassing agents were also examined. While the flow agents had little effect on the rate of polymerization, the degassing agent significantly hampered the polymerization rate.