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Site-selective modification of cellulose nanocrystals with isophorone diisocyanate and formation of polyurethane-CNC compositesAuthor(s): Natalie M. Girouard; Shanhong Xu; Gregory T. Schueneman; Meisha L. Shofner; J. Carson Meredith
Source: ACS Applied Materials & Interfaces 2016, 8. pp. 1458−1467
Publication Series: Scientific Journal (JRNL)
Station: Forest Products Laboratory
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DescriptionThe unequal reactivity of the two isocyanate groups in an isophorone diisocyante (IPDI) monomer was exploited to yield modified cellulose nanocrystals (CNCs) with both urethane and isocyanate functionality. The chemical functionality of the modified CNCs was verified with ATR-FTIR analysis and elemental analysis. The selectivity for the secondary isocyanate group using dibutyl tin dilaurate (DBTDL) as the reaction catalyst was confirmed with 13C NMR. The modified CNCs showed improvements in the onset of thermal degradation by 35 °C compared to the unmodified CNCs. Polyurethane composites based on IPDI and a trifunctional polyether alcohol were synthesized using unmodified (um-CNC) and modified CNCs (m-CNC). The degree of nanoparticle dispersion was qualitatively assessed with polarized optical microscopy. It was found that the modification step facilitated superior nanoparticle dispersion compared to the um-CNCs, which resulted in increases in the tensile strength and work of fracture of over 200% compared to the neat matrix without degradation of elongation at break.
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CitationGirouard, Natalie M.; Xu, Shanhong; Schueneman, Gregory T.; Shofner, Meisha L.; Meredith, J. Carson. 2016. Site-selective modification of cellulose nanocrystals with isophorone diisocyanate and formation of polyurethane-CNC composites. ACS Applied Materials and Interfaces. 8: 1458−1467.
Keywordscellulose nanocrystal, nanoparticle modification, isocyanate chemistry, thermal stability, polyurethane, polymer nanocomposite, dispersion, mechanical properties
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