The Role of Free Magnesium in Natural Rubber Latex Stability

Manufacturer: We are both producers of NR latex concentrate and latex-dipped products. Recently, we have had some debates among ourselves regarding the role of magnesium in the latex in terms of its colloidal stability. Will appreciate your simple advice.

John Woon (Senior Latex Consultant): The presence of magnesium in the final latex concentrates can lead to instability of the latex because it can react with the protective stabilizers (soaps) around the rubber particle surface, rendering them insoluble. Soaps must be in a soluble form for them to work.

The residual magnesium in the latex concentrates can also react with the naturally occurring phosphate in the latex. The phosphate is the result of the hydrolysis of phospholipids in the latex.

In some cases, it can form “magnesium crystallites” that could weaken the dried latex film, causing weakness of the rubber film and the formation of pinholes in condoms, toy balloons, and medical gloves.

The problem is that the ratio of magnesium to phosphate in the latex varies from clone to clone and sometimes within the same clone. And the problem of magnesium is particularly bad during the “wintering” periods.