The Effect of Zinc Distribution on the Mechanical Stability of NR Latex Concentrates

Abstract Dithiothreitol (DTT) has been found to increase the mechanical stability of natural rubber (NR) latex concentrates, particularly in the case of low ammonia TZ (LATZ) latices. The DTT interacts with the zinc on the rubber particle surface to form an insoluble phase which then precipitates in the sediment phase of the latex. Zinc ions tend to destabilize latex by neutralizing some of the fatty acid anions and proteinate anions on the rubber particle surface and DTT increases the stability of latex by removing a large proportion of these zinc ions. The metal complexing agent EDTA is even more effective than DTT at increasing the mechanical stability of LATZ latex. EDTA removes all the zinc from the particle surface and also solubilizes zinc in the sediment, possibly liberating fatty acid anions from the sediment which could then stabilize the latex further. This effect may be useful because it provides a means of increasing or maintaining the stability of LATZ latex when addition of a surfactant is ...