Preparation of latex foam rubber. The Dunlop process was used to prepare the latex foam rubber. Two types of foam of different densities were prepared, namely natural rubber latex foam and blends of NRL and PUD foam of 70:30 ratio.
About 500 grams of NRL or blend compound was mixed with a frothing aid – potassium oleate to reduce the surface tension of the latex mix and poured into a whisk and bowl type mixer to commence whipping. During the foaming operation, an increasing amount of air is included and the viscosity of the foam rises continually. After the desired froth height has been achieved, the secondary gelling agent – diphenylguanidine was added to sharpen up the gelling. This was followed by addition of zinc oxide. Zinc oxide plays a role in the destabilisation or gelling of the latex through formation of zinc soaps13,14. Finally the gelling agent sodium silicofluoride