Stability of melamine formaldehyde (MF) resin under different pH and ionic strength values
Melamine and melamine formaldehyde (MF) resin are both commonly used materials in food technology. It is shown in this work that the stability of aqueous solutions of MF resins during storage is strongly influenced by the ionic strength and the pH value of the suspending medium. Aggregation phenomena, polymerization, or disintegration of MF resin particles can take place. The critical aggregation concentration (CAC 1.67 x 10 2 M KNO3) and the rate constant kapp (1.24 x 10 23 ml/s) for the bimolecular process of aggregation are determined. When the electrolyte concentration is very close to the CAC, the aggregation is slow. By increasing the electrolyte concentration the aggregation process is faster. In high values of ionic strength the aggregation happens almost immediately. At low pH values aggregation phenomena and split of the MF in smaller particles can influence the stability of MF resin particles. For this study, field flow fractionation technique was used. PRACTICAL APPLICATIONS: The present work investigates the role of ionic strength and pH on the stability of melamine. It is shown that aggregation phenomena, polymerization, or disintegration of MF resin particles can take place. Both, aggregation phenomena and split of the MF in smaller particles can influence the stability of MF resin particles at low pH values. These results show that dishes and kitchen utensils made of melamine resins could release melamine when used for acidic foods. The results of this work could be of great importance for both consumers and industry, since they concern preservation, construction, manufacturing, and use of common housewares.