In our concept, the production of thermoset polymeric foam will be possible if the resin gelation induced by the crosslinking reaction and the gas production due to the blowing agent decomposition are able to produce in the same temperature range. Moreover, the definition of the temperature that leads to equilibrium between the kinetics of both phenomena is of first importance for producing rigid and lightweight foams. Indeed, if the crosslinking of the reactive mixture prevails (formulations characterized by a very short gel time), the formation and growth of the cells is can be hindered by a sudden viscosity increase of the resin. Inversely, if the kinetics of decomposition of the blowing agent predominates, formed cells do not remain trapped in the resin because of the low viscosity of the reactive formulation and its excessive gel time. At the same time, the endothermic decomposition of NaHCO3 must not prevent curing reaction that is thermally activated. The experimental data reported in Fig. 10 are useful to guide the choice of the process parameters. The dashed curve represents the first derivative versus temperature of the residual weight of the blowing agent (DTG curve). The same figure also shows the influence of both curing temperature and chemical composition of the resin on its gel time.