Date of Award
Master of Science in Chemical Engineering - (M.S.)
Chemical Engineering, Chemistry and Environmental Science
Wing T. Wong
A polymer dispersion of fluorocarbon with solid constent in the range of 10-25% were prepared from white powder polytetrafluorethylene (PTFE), emulsifier combination of dodecylbenzyldimetlyl sulfonium chloride and Trition N-150, and other components or additives. Such a fluorocarbon dispersion is very stable against coagulation and has a pH in the range of 8-10, which is especially suitable for powder coating purpose.
A new electrocoating technique, which is called cathodic electrodeposition powder coating method, was conducted in this study. This new coating method includes four steps: pretreatment, electrocoating, drying and baking. Two kinds of degreased metal substrates, aluminum and steel plates, were used as the cathode, while platinum was chosen as the anode in the electrocoating step. The electrocoated metal plates were subsequently dried and baked to give final transparent PTFE thin films on the metal surfaces.
Concentration coagulation would be suitable mechanism to explain the film growth of cathodic electrodeposition from PTFE dispersions. Studies of variation of film thickness with deposition time show that the film thickness at all the applied voltages used increased fastly with deposition time until the insulating characteristic started taking place to reduce the rate of film growth. Eventually, a constant ultimate film thickness was reached indicating no further deposition. Furthermore, Infrared spectrum of baked PTFE film was also measured and matched with that of PTFE melt from literature.
Wu, Wen-Lin, "The kinetics and mechanism studies of a polymer powder coating on metal surface by cathodic electrodeposition process" (1986). Theses. 2010.