Green Biomass Materials in Polyurethane Foams

Flexible polyurethane foams were prepared using naturally derived materials as alternatives to conventional auxiliary blowing agents. This research was based on the concept held by some that natural chemicals are better as a part of industrial ecology. The authors have attempted to define the foam manufacturing suitability of natural chemicals, but have not defined or defended the policy implications of such choices. Natural chemicals are often less suitable than those refined from petroleum and may then need some environmental credit related to greater discharge to be viable substitutes. Modest decreases in density (relative to foams without any auxiliary blowing agent) were obtained with the addition of solid CO₂ but other physical properties were not measured. It is unclear whether the reduction in density is a result of the phase change of CO, from solid to liquid within the polyurethane cell matrix or simply a bubbling effect of C02 in solution causing voids within the final product. Although it was anticipated that the high boiling point of limonene, from citrus peeis, would negate effectiveness as an auxiliary blowing agent, there were analogous decreases in foam density. The observed effect might be rationalized by the significant vapor pressure of limonene at temperatures lower than the boiling point. The limonene may be sweptf rom the foam system coincident with the loss of in situ generated CO₂ isoprene, naturally emitted from deciduous vegetation as well as from the combustion of carbonaceous fuels, provides a useful, if not complete, range of foam densities and may then be a partial substitute for halogenated auxiliary blowing agents. Switching from methyiene chloride to isoprene as the auxiliary blowing agent of choice would immediately decrease organic emissions from polyurethane foam plants by 20 percent (molecular weight effect). Regulation as a VOC and the residual acrid odor may be potential drawbacks to commercial utilization of isoprene.