Hydration-Induced Reinforcement of Rigid Polyurethane-Cement Foams: the effect of the co-continuous morphology on the thermal-oxidative stability

The flame retardancy of a new composite polyurethaneecement foams based on the innovative concept of “Hydration-Induced Reinforcement of Polyurethane Rigid Foams”, HIRPeC, through the formation of an organiceinorganic co-continuous morphology have been investigated. The hybrid foams were prepared by allowing polyether polyol mixed with catalysts, surfactants and cement (up to final weight of 60 wt%) to react with Metylen-Diphenyl-Diisocyanate without flame retardant. The composite foams were then cured at 60 C in water for 72 h in order to hydrate the anhydrous cement particles. The hydrated cement phases engender a co-continuous structure within the polyurethane matrix. For comparison both neat polyurethane foams and flame retardant filled foams were also prepared. The composite and the hybrid foams were characterized by X-ray diffraction, mechanical compressive testing and the scanning electron microscopy, while the thermal-oxidative properties were characterized by thermogravimetric analysis. Cone calorimeter analysis which allowed to determine the key properties of thermal degradation, namely the heat release rate, the smoke and CO production from foam combustion. The hybrid foams exhibit a significant improvement of mechanical properties due to the hydration of the cement particles as compared to the un-hydrated composite foam. The results of the thermal characterization showed that the presence of the amounts of inorganic cement particles, alongside with the formation of a co-continuous morphology, produces enhancements of fire behavior and improvements in the thermal-oxidative stability of polyurethane. The flame retardancy who essentially due to the physical action of the inorganic phase which constitutes a barrier at the surface and opposes to the diffusion of volatiles and oxygen.