Abstract
Global sustainability challenges prompt the world to modify its strategies and shift from a fossil-fuel-based economy to a bio-resources-based one and to the production of renewable biomass chemicals. Depolymerized suberinic acids (SA) were considered as an alternative resource to develop bio-polyols that can be further used in polyurethane (PU) material production. Birch (Betula pendula) outer bark was used as a raw material to obtain the SA, extracted with ethanol, and depolymerized with potassium hydroxide ethanol solution. By acidifying the filtrate to pH 5.0, 3.0, and 1.0 and drying it at 50 °C and 130 °C, 12 different SA potential feedstocks were obtained and characterized using chemical (total phenolics content, solubility in DMSO, acid, hydroxyl, and saponification number) and instrumental analytical methods (GC-MS, SEC-RID, DSC, and FTIR). Several bio-polyols were synthesized from the SA sample acidified to pH 1 and dried at 130 °C. Acid number and hydroxyl number values, the apparent viscosity and moisture content were measured. It was concluded that SA have a high enough saponification and acid value to investigate the polyol synthesis route via the esterification reaction. Moreover, SA had OH groups in their structure, which can be exploited for PU material development. The majority of SA compounds had relatively low molecular weight with <1300 Da that are suited for bio-polyol synthesis applied for rigid PU foam development. The synthesized bio-polyols had high hydroxyl number values necessary for bio-polyols to be used for rigid PU foam production.
Highlights
The European Union (EU) recognizes that bio-based materials are critical to the creation of a more circular and decarbonized economy as well as the transition from a fossil to a bio-based economy
The obtained bio-polyols were characterized for hydroxyl and acid values according to the analytical methods using titration as described previously for suberinic acids (SA) characterization in Sections 2.4.2 and 2.4.5, respectively
The obtained bio-polyols were characterized for hydroxyl and acid values according to the analyticalofmethods using titration as described previously for SA characterization
Summary
The European Union (EU) recognizes that bio-based materials are critical to the creation of a more circular and decarbonized economy as well as the transition from a fossil to a bio-based economy. The development of advanced new materials and technologies for bio-based products is critical as the world faces a growing number of issues, leading to growing public awareness about global sustainability. The potential of the available bio-resources in value-added sectors still needs to be fulfilled by new approaches. The majority of polyurethane (PU) materials are obtained from non-renewable feedstock, which is not in line with the directions (sustainable and inclusive economic development and circularity) along which the EU intends to further develop in the upcoming decades. The most promising way to introduce sustainable feedstock into rigid PU foam is to replace one of its components—petrochemical polyols—with a bio-based alternative
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