Blending NR latex with SBR

Manufacturer:  We are manufacturing dipped transparent Natural Latex products. We would like to reduce the product cost by blending with synthetic lattices. We tried using XSBR but  did not get transparency and the product was very weak in strength. Can you suggest any idea to reduce the cost of product by maintaining the transparency and if the strength is reduced marginally then there is no problem. (John Woon's note: Other details not revealed here)


John Woon (Senior Latex Consultant): The physical properties of SBR (Styrene butadiene copolymer) changes progressively from polybutadiene which is flexible and rubbery to polystyrene which is rigid and glassy. I suggest you try those grades with styrene content of 45% and lower. A suitable grade could a high solid (~62%) SBR used for latex foam manufacturing, not XSBR which is carboxylated.

Generally, once you blend NR with SBR you'd get lower tensile strength. Your total rubber content in your latex compound formulation should not change, otherwise you've to adjust the sulphur and accelerator content accordingly.

For maximum transparency, you should select a grade of SBR with a refractive index close to that of NR, i.e. 1.519.

The accelerator you use is not ideal for transparency. You should choose one that's more soluble in rubber and has minimal tendency to bloom.