Thickeners for Natural Rubber Latex

Manufacturer: We are making NR latex compounds and adhesives for backing textiles and rugs/carpets. Very often we are facing "strike-through" problems due to the low viscosity of our compounds. We are now looking into increasing the viscosity of the compounds. Please give us some guidance on the use of thickeners.

John Woon (Senior Latex Consultant): Viscosity of latex compounds (NR or synthetic latices) is very import in controlling the flow, wetting and penetration of the latex on the various substrates such as textile, carpets and rugs. Too low a viscosity would lead to "strike-through" as encountered by you while too high a viscosity would lead to insufficient penetration resulting in poor bonding of the fibres.

There is a wide range of thickeners you could try. The more popular ones include high-molecular weight polymers such as polyacrylates (e.g. ammonium polyacrylate) and modified celluloses (e.g. cellulose ether and hydroxy cellulose ether). Some of the more important factors you should consider in choosing your thickeners are as follows:

1) The ease of dissolution of the thickener in water if it is available in powder form. Of course, a ready-to-use solution is preferred for obvious reason.

2) The compatibility with the latex compounds. It should not cause destabilization the the latex.

3) The stability of viscosity of the stock solution. It should not increase or drop on storage.

4) Efficiency of the thickener i.e. it should give maximum viscosity at minimal addition level.

5) Stability of the viscosity of the thickened latex compounds. This should not vary with time otherwise you might get inconsistent coating and penetration.