Vulcanisation and thickening of positively charged Natural Rubber and Nitrile latices (latexes)

Manufacturer: We managed to produce positive charged natural rubber latex and Nitrile latex. This is for coating and impregnating textiles which usually have negative charges. To our satisfaction, we found the adhesion of the latex to the textile to be superior compared to normal centrifuged natural rubber latex concentrates (i.e. CL 60 HA or LATZ) and standard Nitrile latex.

However, our problem is that the ageing resistance of the rubber is quite poor. To overcome this we decided to add curing agents to vulcanize the rubber. However we encountered latex stability problem during mixing of the latex compounds. Also, we had problems when we intended to increase the latex viscosity with acrylic types of thickener.

Your suggestions on how we could overcome these problems would be appreciated.


John Woon (Senior Latex Consultant): If you are using conventional dispersing agents for the preparation of your curative dispersions or you are using ready made dispersions from external sources, I won’t be surprised at all that you’re experiencing the latex stability problem you mentioned.

You should use only cationic surfactants and perhaps along with only non-ionic surfactants as your dispersing agents because your latex particles are positively charged, unlike the usual natural rubber and nitrile latex concentrates. Examples of the former are quaternary ammonium compounds such as cetyl trimethyl ammonium chlorides and cetyl pyridium bromide while examples of the latter are condensation products of ethylene oxide with fatty acids, alcohols or phenols.

As regards the latex thickeners, you should not use anionic type like sodium or ammonium polyacrylates. Your better bet should be those based on methyl cellulose.







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