Water Resistance of Rubber Products

Manufacturer: One customer of ours is asking for the status of water resistance of our products. I thought natural rubber is water repellent by nature. Why is this requirement necessary?

John Woon (Senior Latex Consultant): You are right in thinking that rubber products are water repellent but please bear in mind that this property for rubber only appears to be superior in comparison to alternative materials such as fabrics, paper, wood and leather.

There is an ASTM standard test for water resistance, similar to the total immersion procedure for oil resistance. Results are usually expressed as weight or volume change of the test specimen.

Compounding ingredients play more important parts than the rubber itself. As far as practically possible one should avoid hydrophilic materials. These water soluble ingredients might also lead to a drop in physical properties after exposure to water, hence the concern of your customer.

You have to ensure your processes include an efficient leaching section. You must use both cold and hot leaching.