Diammonium Phosphate (DAP) and Latex Stability

Manufacturer: We are latex concentrate producer. In our attempt to control the level of magnesium, what would happen if we over add DAP?

John Woon (Senior Latex Consultant): Field latex must be treated with sufficient Diammonium phosphate (DAP) to get rid of the harmful magnesium. However, over addition of DAP could destabilize the latex. 

It had been reported that an MST of 1200 seconds could drop to 300 to 500 seconds, after adding 0.5% to 1.0% of DAP to a normal latex concentrate.

Magnesium in Natural Rubber Latex and Latex Stability

Manufacturer: Magnesium level is not a requirement in our standard for NR latex. Do you think we should measure this? What happens if the magnesium level is too high, say, more than 50ppm?

John Woon (Senior Latex Consultant): The presence of magnesium in the latex concentrates can lead to instability of the latex because it can react with the soaps around the rubber particle surface, resulting in the destabilization of the latex. Therefore, it is advisable to conduct test to determine the magnesium level.

In some cases, magnesium can form “magnesium crystallites” that can result in pinholes in condoms, toy balloons, and medical gloves. Ideally, the magnesium level  in latex concentrates should be less than 35 ppm.