Center for Plastics Innovation
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Browsing Center for Plastics Innovation by Author "Epps, Thomas H. III"
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Item Lignin-derivable, thermoplastic, non-isocyanate polyurethanes with increased hydrogen-bonding content and toughness vs. petroleum-derived analogues(Materials Advances, 2024-04-02) Mahajan, Jignesh S.; Hinton, Zachary R.; Nombera Bueno, Eduardo; Epps, Thomas H. III; Korley, LaShanda T. J.The functionality inherent in lignin-derivable bisguaiacols/bissyringols can improve the processability and performance of the resulting polymers. Herein, non-isocyanate polyurethanes (NIPUs) were synthesized from bisguaiacols/bissyringols with varying degrees of methoxy substitution and differing bridging groups. Notably, the presence of increasing numbers of methoxy groups (0, 2, and 4) in bisphenol F (BPF)-, bisguaiacol F (BGF)-, and bissyringol F (BSF)-NIPUs led to higher percentages of hydrogen-bonded –OH/–NH groups (i.e., ∼65%, ∼85%, ∼95%, respectively). Increased hydrogen bonding between chains improved the elongation-at-break (εbreak) and toughness of lignin-derivable NIPUs over their petroleum counterparts without a reduction in Young's moduli and tensile strengths. For example, BSF-NIPU exhibited the highest εbreak ∼210% and toughness ∼62 MJ m−3, followed by BGF-NIPU (εbreak ∼185% and toughness ∼58 MJ m−3), and then BPF-NIPU (εbreak ∼140% and toughness ∼42 MJ m−3). Similar trends were found in the dimethyl-substituted analogues, particularly for the bisphenol A-NIPU and bisguaiacol A-NIPU. Importantly, the melt rheology of the lignin-derivable NIPUs was comparable to that of the petroleum-derived analogues, with a slightly lower viscosity (i.e., improved melt flow) for the bio-derivable NIPUs. These findings suggested that the added functionalities (methoxy groups) derived from lignin precursors improved thermomechanical stability while also offering increased processability. Altogether, the structure–property-processing relationships described in this work can help facilitate the development of sustainable, performance-advantaged polymers.Item Oxidative Functionalization of Long-Chain Liquid Alkanes by Pulsed Plasma Discharges at Atmospheric Pressure(ACS Sustainable Chemistry and Engineering, 2022-11-17) Nguyen, Darien K.; Dimitrakellis, Panagiotis; Talley, Michael R.; O'Dea, Robert M.; Epps, Thomas H. III; Watson, Mary P.; Vlachos, Dionisios G.We introduce the oxidation of long aliphatic alkanes using non-thermal, atmospheric plasma processing as an eco-friendly route for organic synthesis. A pulsed dielectric barrier discharge in He/O2 gas mixtures was employed to functionalize n-octadecane. C18 secondary alcohols and ketones were the main products, with an optimal molar yield of ∼29.2%. Prolonged treatment resulted in the formation of dialcohols, diketones, and higher molecular weight oxygenates. Lighter hydrocarbon products and decarboxylation to CO2 were also observed at longer treatment times and higher power inputs. A maximum energy yield of 5.48 × 10–8 mol/J was achieved at short treatment times and high powers, associated with higher selectivity to primary oxygenates. Direct hydroxylation of alkyl radicals, as well as disproportionation reactions, are proposed as the main pathways to alcohols and ketones. The results hold promise for functionalizing long hydrocarbon molecules at ambient conditions using catalyst-free plasma discharges.