Polyurethane foams made from liquefied bark-based polyols



Liquefaction is known to be an effective method for converting biomass into a polyol. However, the relationships between bark liquefaction conditions and properties of the resulting foams are unclear. In this study, polyurethane foams (PUF) were made using bark-based polyols obtained through liquefaction reactions of bark at two different temperatures (90 and 130°C). Through systematic characterization of the PUFs the influence of the liquefied bark and liquefaction conditions on foam properties could be observed. The bark-based foams had similar foaming kinetics, thermal stability, and glass transition temperatures compared with the PEG-based control foam. The bark-based PUF from the polyol obtained at the higher liquefaction temperature showed comparable specific compressive strength to the PEG-based control foam. Lastly, both bark foams exhibited a high amount of open-cell content, with the foam made from the lower temperature liquefied polyol having poor cell morphology. This deviation from the controls in the open-cell content may explain the lower modulus values observed in the bark PUFs due to the lack of cell membrane elastic stretching as a strengthening mechanism. These results demonstrated the influence of the bark liquefaction conditions on foam properties, thereby providing a better fundamental understanding for the practical application of bark-based PUFs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40599.