(636h) Synthesizing Thermosetting Polymers from Birch Bark Extract

Modern polymeric materials are often derived from petroleum, a long-term non-sustainable resource. Conversely, bio-based alternatives can be produced from naturally grown sources with inherent attributes. Birch tree barks have been regarded as waste in the papermaking industry and are typically burned as a low-grade fuel. However, this substance contains many valuable chemicals that can be functionalized and polymerized into bio-based materials, such as triterpenoids, consisting of betulin, betulinic acid, and lupeol, as well as lignin, polysaccharides, and suberin. These substances offer additional hydrophobicity that could benefit birch bark extract-based polymeric materials in many applications, such as coatings and adhesives. Research has shown that betulin-based thermoplastics have promising mechanical and thermal properties; however, obtaining pure betulin requires many costly purification steps. Therefore, we proposed the utilization of birch bark extracts as raw materials to synthesize polymeric materials to minimize the number of steps in material acquisition. For comparison, the birch bark extracts (BBE) were obtained through lab-scale Soxhlet extraction using selected solvents such as chloroform, ethanol, and ethyl acetate. Molecular characterization of the extract was completed using proton NMR, advanced polymer chromatography (APC), high-performance liquid chromatography (HPLC), and hydroxyl value titration to confirm and characterize the presence of the chemicals of interest. Bio-based polyester thermosets were synthesized from the obtained BBEs. A variation in chemical composition was detected based on the selected solvents and season. The processing-structure-property relationship of the bio-based polyester thermosets was established, along with initial techno-economic analysis results. By strategically combining the characteristics of BBEs with other bio-based molecules, we present a viable solution that minimizes manufacturing costs and affords more environmentally-friendly and sustainable polymeric materials.