| As the air conditioner is minimizing, the heat-exchanger fin is requested to have better properties such as good hydrophilicity and alkali resistance. It is proved that hydrophilic coating and alkali resistance coating is an effective way to reach the goal. First, a hydrophilic coating based on water-soluble resin was prepared by copolymerizing of acrylic acid (AA), acrylic amide (MA) and 2-acrylamido-2- methylpropancsulfonic acid (AMPS). The initiator system is (NH4)2S2O8-NaHSO3. The suitable ratio of AA:AM:AMPS is 5:3:2, and the suitable polymerization conditions are: polymerization temperature is 30℃ and time is 1 hour. The coating prepared at such condition has an excellent hydrophilicity. The contact angle(water / coated film) is 13.22°. It is found that the main factor affecting the hydrophilicity of the coating is AA, the next one is AMPS, AM shows a little effect on the hydrophilicity of the coating.According to the theory of molecular design, a water-soluble coating based on epoxy resin was prepared by introducing quaternary ammonium salt to the main chain of epoxy resin. It is found that extension for time or raising the reaction temperature, the alkali resistance, the cold-hot circulation resistance, solvent resistance and water resistance of coating are increased. But its hydrophilicity decline. On the other hand, increasing the consumption of quaternary ammonium salt can increase the hydrophilicity of the coating, but its alkali resistance, cold-hot circulation resistance, solvent resistance and water resistance of this coating decline. Considering all factors the suitable reaction condition is :polymerization temperature is 105℃, the mole ratio of quaternary ammonium salt to the of epoxy group is 0.75:1,the reaction time is 4 hours. Alkali resistance of the coating prepared under such condition (20%NaOH solution) is more than 60 minutes.
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