Synthesis and characterization of bio-polyols through the oxypropylation of bark and alkaline extracts of bark

Bark and alkaline extracts of bark were oxypropylated to produce bio-polyols. It was found that bark had a much higher yield (79%) than the alkaline extracts (32%). Solvent extraction and thermo-gravimetric analysis showed that the homopolymer helped reduce viscosity and that the co-polymer showed evidence of grafting. As a result, the bark derived bio-polyols had a very low viscosity, especially compared to reported values for other types of biomass that produced prohibitively highly viscous liquids. GPC analysis showed that high molecular weight compounds from bark were made highly soluble by the grafting of PO chains. This resulted in a molecular weight average of 6800 Da for the oxypropylated bark, and 7100 Da for the alkaline extract of bark. The hydroxyl value and high concentration of secondary alcohols in the bio-polyols was consistent with typical commercial polyols used for rigid foam formulations. Finally, when foamed, the oxypropylated bark-based foam showed superior compressive behavior to previous work done on liquefied bark-based PUFs and a control foam. (C) 2015 Elsevier B.V. All rights reserved.