Synthesis and Characterization of Novel UV-curable Fluorinated Polyurethane-acrylate Copolymer

A series of UV-curable fluorinated polyurethane-acrylate（PUA） has been developed by incorporating octafluoropentyl alcohol into the segment of UV-curable polyurethane-acrylate to improve the thermal property and surface property of the copolymer material. The structures of the synthesized polymers were characterized by Fourier transform infrared（FTIR） spectrometry. In order to find out the effect of incorporated fluorine on the UV-cured films, the properties of the UV-cured films were tested through contact angle, water absorption, and thermogravimetric analysis （TGA）. The fractured-surface morphologies of the UV-cured coatings were investigated by scanning electron microscopy（SEM）. With increasing the content of fluorine segments, the contact angle of the UV-cured films increased and the water absorption decreased, suggesting the fluorine segments migrated and formed a fluorine-covered surface to avoid water penetration. The observation of the fractured-surface morphology through SEM test showed that the fluori- nated UV-cured films gained rough fractured-surface compared with the pure UV-cured polyacrylate film, demonstrating the migrating of the fluorine segments. The TGA curves show that the fluorinated UV-cured films gained higher thermal degradation temperature than the virgin UV-cured polyacrylate film. And as increasing the fluorine content, the thermal degradation temperature increased. These phenomena could be reasonably explained by the enrichment of fluorinecontained segment on the surface of the film and the high thermal property due to fluorine atom.

Oligo-fluoropolymer Modified Cycloaliphatic Epoxy Resins with Excellent Compatibility, Waterproof and Mechanical Properties for LED Encapsulation

An oligo-fluoropolymer（PFM） with functional cycloaliphatic epoxy and fluorinated groups was obtained via free radical polymerization and applied to the modification of cycloaliphatic epoxy resins（CE）. The chemical structure of PFM was characterized by Fourier transform infrared（FT1R） spectroscopy, gel permeation chromatogra- phy（GPC） and nuclear magnetic resonance（NMR） spectroscopy, and the effects of different PFM concentra- tions（0.5%-6%, mass fraction） on the thermal resistance, mechanical properties, surface dewettability, light trans- mission, refractive index and various cured polymer properties were studied ha detail. The DSC and TGA results demonstrate that the modified epoxy resins possess a higher thermal resistance than the neat epoxy resin. The im- provements in the surface dewettability and water resistance are caused by the high crosslinking density and the enrichment of the oligo-fluorinated random copolymers dispersed in the matrix. The fracture surface morphologies of the thermosets were investigated by scanning electron microscopy（SEM） and transmission electron microsco- py（TEM）. It was observed that the optical transmittance of the composites was maintained even though microphase separation occurred during the curing process. With respect to the corresponding properties of the neat epoxy resins, the 2 phr（parts per hundreds of resin） PFM thermoset exhibited relatively better comprehensive properties, making the cured material a good candidate for light-emitting diode（LED） encapsulation.