A Practical Approach to Cleaning Molds from Rubber Residues

In this paper, methods of fouling prevention and cleaning of the molds from vulcanized rubber residues are presented. The surface free energy of mold surfaces has been measured and the mold release agents were compared by measuring the force needed for the release of the form. The efficiency of sodium hydroxide solvent currently used for mold cleaning in industrial practice is compared with an acid-based solvent. The effect of the acid on the mold surface is monitored as well. The relative mass loss and the change in the surface roughness parameters Sa and Sz were evaluated during the corrosion testing in the acid at various temperatures. The mold wear during a year of use in the company, and a year of continuous acid exposure was then extrapolated for steel and stainless-steel molds. Nitric acid was significantly more effective than NaOH in dissolving rubber with full dissolution occurring after 3 h at 80°C when stirred, losing 33 % of its initial mass, while NaOH lost only 0.3 % after 24 h. Stainless steel proved very resistant to acid corrosion at 50°C with a calculated loss of 0.003 cm of thickness per year of submersion, while 1.7131 steel would lose 0.264 cm of thickness.