The Hydrophilic Modification Of Polypropylene Substrate Used For Electrostatic Precipitator

Metal plates used as the dust collecting electrode of an electrostatic precipitator show low corrosion resistant and low cost competitive,and if polypropylene is used instead,its hydrophobicity and non-conductivity must be improved.Concerning the problems in this paper,Ni-P alloy coating and Ni-P-?n-Al₂O₃?composite coating were prepared on polypropylene substrate by chemical plating,aimed at changing the surface properties of polypropylene like hydrophilicity and corrosion resistance etc.,for the replacement of the metal plates with modified polypropylene.?1?The optimal preparation processes of Ni-P alloy coating and Ni-P-?n-Al₂O₃?composite coating were obtained by comparing the deposition rate and coting structure at different process condition.The optimized preparation parameters for Ni-P alloy coating were NiSO₄·6H₂O 30 g/L,C₆H₅O₇Na₃·2H₂O 25 g/L,NaH₂PO₂·H₂O 30 g/L,NH₄Cl 30 g/L,?H₄N?₂S 5 mg/L,pH 9.0,45?and 30 min and the ones for Ni-P-?n-Al₂O₃?composite coating were NiSO₄·6H₂O 30 g/L,C₆H₅O₇Na₃·2H₂O 25 g/L,NaH₂PO₂·H₂O 30 g/L,NH₄Cl30 g/L,nanoAl₂O₃ 7 g/L,surfactant 0.5 g/L,?H₄N?₂S 5 mg/L,pH 9.0,45?and 30 min.?2?Ni-P alloy coating has both crystalline structure and non-crystalline structure and Ni-P-?n-Al₂O₃?composite coating is composited of only non-crystalline structure.?3?Nano-Al₂O₃ was detected in Ni-P-?n-Al₂O₃?composite coating.Nano-Al₂O₃ in composite coating can refine grains,improve the surface morphology and density of the composite coating,enhance the microhardness of Ni-P alloy coating.But excessive addition of n-Al₂O₃ can cause agglomeration of n-Al₂O₃ and result in the decrease of coating hardness.?4?It was shown that the adhesion of Ni-P-?n-Al₂O₃?composite coating was excellent detected by crossing and thermal shock method.The corrosion of Ni-P-?n-Al2O3?composite coating was better than that of Ni-P coating measured by HNO₃ drop method.?5?The experimental results showed that the contact angle of Ni-P alloy coating and Ni-P-?n-Al2O3?composite coating freshly prepared decreased significantly after a period of time.When properly treated,surface contact angle of the coatings reduced to 20°to 60°,which basically returned to the original level.