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 degrees 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. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40599.