How to improve resistance to air permeability of Natural Rubber latex products?

Air Bladders Manufacturer: We manufacture a range of bladders using natural rubber latex. For some products the air permeability is too high resulting in premature deflation and therefore failure of the products. Can you suggest some quick solutions?

John Woon (Senior Latex Consultant): This question has been raised and answered at this site before.

If you don't already know, natural rubber has quite poor resistance to air permeability compared to most synthetic rubbers. You could try blending NR latex with other synthetic rubber latices such as Polychloroprene (e.g. Neoprene) and Nitrile latex but this normally requires quite a high level of the synthetic latex leading to the undesirable loss of flexibility, resilience and elongation.

Your best bet is to do "laminate dipping" whereby an over-dip with synthetic latex is carried out after the first NR latex dip. The sequence of the two dips can be changed depending whether you want the synthetic layer to be the external or internal surface. Products with an external polychloroprene layer could also render the products more resistant to ageing especially against ozone attack.

To further enhance the air impermeability, you could also add some laminar types of fillers an example of which is silica.

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