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UBC Theses and Dissertations

The characterization of acetone fractionated and unfractionated, chemically modified lignin-Ecoflex™ thermoplastic blends Bessler, Kim


There is a growing demand to replace non-renewable fossil-based materials like many one use plastics with renewably sourced alternatives that fit within the circular bioeconomy model and demonstrate a favourable end of life. One such option is lignin, found in all woody plants with its desirable aromatic polymeric structure and potential utilization as a byproduct in the pulping and paper industry. However, complications arise because of lignins’ complex non-uniform heterogenous structure which is often remedied through harsh carcinogenic chemical pathways. In this study softwood kraft lignin was fractionated in a one step process using acetone, modified first with ethylene carbonate, then with propionic acid, and finally melt-blended with completely biodegradeable Ecoflex™ in order to develop an alternative to thermoplastics like non-degradable polyethylene and polypropylene. The acetone fractionation separated the lignin by molecular weight. The reaction with ethylene carbonate etherified the lignin creating a more uniform structure. Finally, the reaction with propionic acid esterified the lignin thus masking reactive hydroxyl groups. Nine lignin powders ready for blend with Ecoflex™ were developed using green chemistry practices: unfractionated (UF), acetone soluble (ASKL) and acetone insoluble (AIKL) fractions each unmodified (UN) and modified via hydroxyethyl ether (HE) and esterification (E). The lignin samples were melt-blended, extruded, mould injected and underwent extensive tensile testing to determine how each fraction with or without modification behaved in comparison to the as received softwood kraft lignin. In addition, detailed thermal and structural testing was carried out using DSC, TGA, and FT-IR analysis. The acetone soluble fraction without modification (ASKL_UN) increased the tensile properties (tensile strength and toughness) at lower lignin loadings (5-10 wt%) in comparison to neat Ecoflex™ and the acetone insoluble fraction. The acetone soluble esterified lignin (ASKL_E) maintained tensile properties up to a 40 wt% lignin loading in comparison to neat Ecoflex™ and the acetone insoluble fraction. In summary, this work used green chemistry practices to develop lignins that were processible with the biodegradeable polyester Ecoflex™ and found an improvement in tensile properties. This has great implication in valorizing lignin-based polymeric materials as this work showed a simple acetone fractionation is capable of improving mechanical properties.

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