Effects of surfactants on the mechanical properties, microstructure, and flame resistance of phenol–urea–formaldehyde foam

To study the effect of surfactants on the foaming behavior of phenol–urea–formaldehyde foam, silicone oil (Dow Corning DC-193) and Tween-80 surfactants were selected to study their effects on the mechanical properties, microstructure, and combustion characteristics of the foams. The results show that the surface tension of the phenol–urea–formaldehyde resins decreased with increasing surfactant concentration. Both the foaming temperature and foaming capacity of the phenol–urea–formaldehyde foam first increased and then decreased with increasing surfactant concentration. The compressive strength and oxygen index of the phenol–urea–formaldehyde foam first decreased and then increased with increasing surfactant concentration, which is probably related to the foaming capacity of the foam. The microstructure of the foams showed that the average pore diameters first increased and then decreased with increasing surfactant concentration. The combination of DC-193 and Tween-80 surfactants significantly improved the compressive strength, uniformity of the cells, and the number of closed cells in the final foam product.