Adhesion of nylon-6 to triazine trithiol-treated metals during injection molding

An examination was made of the adhesion of nylon-6 resin to treated metals such as phosphor bronze, brass plates, and electronickel platings during in jection molding. No adhesion to any of these metals was noted to occur unde r ordinary injection molding conditions and an aqueous solution of 1,3,5-tr iazine-2,4,6-trithiol mononatrium (TTN) was thus used to induce adhesion. F ollowing treatment with aqueous TTN solution under optimal conditions, nylo n-6 adhered tightly to all the above metals under ordinary injection moldin g conditions. The TTN treatment led to the formation of surface films conta ining metal salts of 1,3,5-triazine-2,4,6-trithiol (TT). Conditions were ma de optimal with regard to time, temperature and TTN concentration. Adherent films were generally formed when bronze and brass were treated for short p eriods, at low temperature, and at low TTN concentration, although this was not the case with nickel plating. There was no adhesion to nickel plating even for a prolonged treatment time, high temperature, and high TTN concent ration. Adherent and non-adherent films did not differ in the chemical stru ctures of the metal salts of TT but they did differ in morphology. Good adh esion was noted in the case of TT-metal salts present at low density on the metal surface. Some films readily reacted with amino compounds under condi tions similar to those generally used for the injection molding of nylon. T he adhesion was concluded to be due to the formation of interfacial bonds d uring injection molding.