Discolouration of Natural Rubber Latex Products

Manufacturer: Can you please explain why products made from natural rubber latex tend to discolour more than synthetic latices?

John Woon (Senior Latex Consultant): Good question. One major causative agent is the naturally occurring enzyme called polyphenol oxidase in the so-called non- rubbers. This tends to darken the coagulated or dried rubber when exposed to air (i.e. oxygen).

Another reason could be the presence of residual "Frey Wyssling" particles which lead to discolouration due to their carotenoid nature. And this accounts for the yellowish colour.

As shown in the diagram, FW = Frey Wyssling Particle, RP = Rubber Particle, L = Lutoid, LVW = Latex Vessel Wall.

Poorly leached products made from natural rubber latex would also tend to darken on storage.