ABSTRACT
The Montreal Protocol regulates the uses of ozone depletion substances (ODSs). In the developed countries, the phaseout of high ozone depletion potential (ODP) CFCs in rigid foam applications was made possible with the introduction of lower ODP HCFCs. HCFC-14 lb was chosen as an excellent replacement for CFC- 11 in many rigid foam applications. HCFC-141b blown rigid foams offer excellent thermal insulation, fire resistance and dimensional stability.
According to the Montreal Protocol, HCFC-141b will eventually be phased out. Lower ODP HCFCs (i.e., HCFC-142b and HCFC-22), zero ODP HFCs and hydrocarbons are considered to be alternatives. Unfortunately, neither HFCs nor pentanes can match performance and cost of HCFCs.
An HFC and pentane(s) coblowing system can potentially offer some advantages over purely pentane blown foams including lower foam density (therefore lower cost), better thermal insulation and better fire performance than purely pentane(s) blown foams. The coblown foam has lower cost than HFC blown foams.
In this study, we choose HFC-134a, a commercially available blowing agent, as a coblowing agent with pentane(s). We make polyisocyanurate (PIR) foams with HFC-134a as a coblowing agent with n-C5, i-C5, i-C5/c-C5, and the levels of HFC-134a are 10 and 20 mole%. We determine thermal conductivity (or k-factor) of foams from −8 to 40 °C. The results show that the effects of HFC-134a on the low temperature k-factors are different, depending on the pentane isomers. Furthermore, we screen a series of surfactants to determine their effects on the k-factors.
