Zinc Oxide Thickening of Natural Rubber Latex Compound

Manufacturer: We are manufacturers of latex dipped products such as gloves and frequently encounter latex stability problems such as increased viscosity in compounds having higher level of ZnO. Among other things, we intend to add non-ionic attractant to counter the thickening of the latex. What possible side effects do you think this strategy would give us?
 
John Woon (Senior Latex Consultant): What you are encountering is what is commonly referred to as "Zinc Oxide Thickening". Non-ionic surfactants of the polyethylene oxide condensate type could help reduce the thickening. This is usually added in conjunction with KOH to maintain a high pH while the use of ammonia is restricted to minimize ammonium salt formation.

However, you must take note of the following negative side effects:

1) It would slow down gelling of latex and hence reducing latex pickup in coagulant dipping process.

2) It affects the gelling of latex extrudate for latex thread manufacturing and hence retarding the formation of solid filament.

3) Some non-ionic surfactants could reduce the mechanical stability of the latex resulting in the formation of coagulum.