Surface Modification Of The Ultrafine PTFE Particles And Self-assembling On Metal Surface

Metal surface multifunctionization has been received great attention in recent years. The modified metal surface can be of perfect property of hydrophobic nature, which can be used in many fields such as scale prevention, anti-contamination, steam dropwise condensation and heat transfer enhancement. In this paper, the surface of the ultrafine polytetrafluoroethylene (PTFE) particles has been activated by sodium-naphthalide solution. The 11-Aminoundecanoic acid [NH₂(CH₂)10COOH] molecules have been grafted on the activated PTFE particle surface in the cetane. Infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) are employed to characterize the activated and grafted ultrafine PTFE particles. The coatings of nickel-phosphor and nickel-copper-phosphor are prepared on the pretreated metal surface by electroless plating technology. The coating surface has been characterized by XPS and SEM. The grafted ultrafine PTFE particles have been self-assembled on the electroless coating of the metal surface. XPS and SEM are applied to characterize the composite metal surface. The results show that: the sodium-naphthalide solution can effectively activate the surface of the ultrafine PTFE particles, and the hydroxyl groups, carbonyl groups and carboxyl groups have been formed on the ultrafine PTFE particle surface after activated in sodium-naphthalide solution. In addition, carbonization has taken place on some parts of the particle surface. The particle surface activation degree can be enhanced dramatically with the appropriate increase of sodium-naphthalide concentration and the activating time. The 11-Aminoundecanoic acid molecules can be grafted onto the modified ultrafine PTFE particle surface through condensing reaction between the amino groups of the 11-Aminoundecanoic acid and the hydroxyl groups on the grafted ultrafine PTFE particle surface. The appropriate augment of the reaction time can promote the graft obviously. The carboxyl groups (offer isolated electrons) of the 11-Aminoundecanoic acid molecules on the modified ultrafine PTFE particle surface can react with the copper and nickel metal atoms (offer empty orbits) on the coating surface and form coordinate bonds, therefore, the ultrafine PTFE particle can be anchored on the metal surface via the carbon chains of the 11-Aminoundecanoic acid, as a result, the metal surface is modified effectively. The number of the ultrafine PTFE particle anchored on the metal coating surface depends strongly on the self-assembled time.