Open Cell Isocyanurate Foams: A Novel Route to High Performance Thermal Insulation Panels

This paper discusses a novel type of rigid foam, open cell isocyanurate foam, and its use as a core material for vacuum insulation panels. Due to the forthcoming phase-out of CFCs, alternative blowing agents are being studied worldwide. It has been well recognised that the total thermal conductivity of closed cell foams consists of the factors as shown below: λ f = λ g + λ s + λ c + λ r where λ f = total λ g = gas λ s = solid λ c = convection λ r = radiation When open cell foams are used as core materials for insulation panels kept under vacuum, the total thermal conductivity of the panel consists of only two factors shown below: λ f = λ s + λ r Therefore, the thermal conductivity of the panels could be far less than that of CFC-blown foams. This paper describes the preparation, processing, properties and applications of open cell rigid isocyanurate foams. The open cellfoams were blown by using a blend of methylene chloride and n-pentane at specific ratios between 95/5 and 50/50 by weight. The resulting foams had open cell contents of about 50-95%, depending upon the reaction conditions employed at densities of 30-50 kg/m3. When pour-in-place foams were further exposed to vacuum after foaming, the resulting foams had an increased open cell content. This open cell foam technology suggests a variety of potential applications, not only for household refrigerators and deep freezers, but also for cryogenic liquidtank insulation, e.g. liquid hydrogen, liquid oxygen, liquid nitrogen, and liquefied natural gas.