chapter  6
Hybrid Polyurethane Nanocomposite Foams
Pages 36

Polyurethane (PU) foams are a family of cellular materials that are used extensively in almost every ambit of application due to their extended range of physical and chemical properties, which depend on the formulation used and processing. Though a great deal of attention has been given to overcoming the relatively low thermal stability and especially poor mechanical properties of polyurethane foams, which have mainly been achieved through the years by the initial replacement of polyester polyols by polyether polyols and later by incorporation of foam catalysts and stabilizers, enabling a vast implementation of one-step polyurethane foaming technologies and thus a general boost in polyurethane foaming, there are still limitations in terms of properties that considerably limit their range of application. For instance, owing to their extremely reduced thermal conductivity, low-density rigid PU foams are used extensively as thermal insulators in the building sector. Nevertheless, the extremely low densities required to achieve such a level of thermal insulation result in significant decreases in terms of mechanical strength, inhibiting the use of these foams in many structural applications.