The introduction of hydrophilic groups, such as -COOH, -SO3, -OH, -O-, into the polyurethane resin, so that waterborne polyurethane products in the water resistance, solvent resistance, weather and other aspects of performance are worse than solvent borne systems. In our work, to improve the water resistance of the films for waterborne polyurethane, we incorporated C=C bond into the side chain of polyurethane by using pentaerythritol diacrylate as an extension agent. By measuring the cured polyurethane films absorption and mechanical properties, we determine the conditions for UV curing, 3% TMPME, photoinitiator (2959) and to UV light application time for 30s. With the increase of the amount PEDA, water resistance, hardness and tensile strength increase. Furthermore, with the improved water resistance, it is hoped that the performance of waterborne polyurethane can be comparative or superior to the solvent-borne systems.
Fuel cells have the great prospect in energy storage technology from the perspective of energy conservation and ecological protection. However, oxygen reduction reaction (ORR) always proceeds sluggishly leads to limited performance. Choosing an excellent ORR electrocatalyst is considered to be an effective strategy. Herein, we have presented an easy synthesis method to prepare highly nitrogen-doped porous carbon nanosheets (HNPC) electrocatalysts. The as-synthesized HNPC electrocatalysts delivered excellent catalytic properties by 4 e – transfer pathway with extremely few HO 2– , due to excellent compositional characteristics (highly N doping) and structural features (porosity). It provides some guidance for the synthesis of excellent electrocatalysts, which will have certain significance for the development of fuel cells.
In this work, PDMS modified PU was synthesized using two-stage method to improve water resistance and weather resistance in the waterborne polyurethane was investigated. It was found that the absorbed water content decreased with increasing PDMS content in polyurethane. It was also found that PDMS modified polyurethane had better solvent resistance than unmodified polyurethane. The structure incorporated the PDMS into the soft segment of polyurethane chains was confirmed by FTIR. The phase separation increased by increasing PDMS content and was confirmed by DSC. The particle size of the dispersions increased and tensile strength and hardness decreased with the increase of PDMS content. Furthermore, with the improved water resistance and elongation, it was hoped that the modified polyurethane could be used as wood coatings superior to the solvent-borne systems.
In this paper three kind of water borne polyurethane are synthesized. FTIR identify the structure of 2-hydroxypropyl acrylate terminated water borne polyurethane with block PDMS. It is found that Si-WPUA has excellent water-resistance, good toughness, and good tensile strength. So, the work has been found the method which could improve water resistance and not decrease mechanical properties. It is hoped that the modified polyurethane could be used as coatings superior to the solvent-borne systems.
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