The concentration of sodium bicarbonate as a chemical blowing agent was
varied to evaluate its effect on the morphology and impact properties of natural rubber
foam. The expandable rubber samples were prepared using a conventional two-roll mill
and were then expanded via a heat transfer foaming process using compression moulding
and an air-circulating oven. The physical properties of the natural rubber foams were
characterised, and the results were observed to systematically correlate with the impact
properties of the foam. The absorbed energy of the foam increases with decreasing
crosslink density and relative foam density, which is associated with the formation of
smaller foam cells and an increase in the number of cells per unit volume
