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    Author(s): Caitlyn M. Clarkson; Sami M. El Awad Azrak; Gregory T. Schueneman; James F. Snyder; Jeffrey P. Youngblood
    Date: 2020
    Source: Polymer. 187: 122101. https://doi.org/10.1016/j.polymer.2019.122101
    Publication Series: Scientific Journal (JRNL)
    Station: Forest Products Laboratory
    PDF: Download Publication  (3.0 MB)

    Description

    In the present study, very small concentrations of CNCs and CNFs were melt-compounded into PLA using a solvent-free process where poly(ethylene glycol) (PEG) was used to disperse the nanoparticles in PLA. As a comparison, the commercial nucleant, talc, was processed similarly into PLA. CNC and CNF were shown to be efficient nucleants for PLA, similar to talc, and conventional Avrami and Lauritzen-Hoffman analysis of the crystallization behavior was performed for isothermal temperatures from 90 °C to 130 °C across all compositions. From the Avrami analysis, the crystallization rate, half-time, and Avrami exponent were calculated and suggested a synergistic effect of nanocellulose and PEG, even at very small concentrations. The crystallization half-time was lower than talc at higher temperatures indicating faster crystallization for samples containing nanocellulose under certain conditions. Analysis of secondary nucleation revealed a decrease in the surface energy for CNC containing samples, further suggesting that, given the enhanced mobility of plasticized PLA, very small concentrations of CNC are effective nucleation agents. Lastly, scanning electron microscopy was used to correlate the crystal morphology of chemically etched samples with the thermal analysis. Coarsening of the microstructure was observed initially with the addition of PEG, and further coarsening was observed upon the addition of nanocellulose.

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    Citation

    Clarkson, Caitlyn M.; El Awad Azrak, Sami M.; Schueneman, Gregory T.; Snyder, James F.; Youngblood, Jeffrey P. 2020. Crystallization kinetics and morphology of small concentrations of cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) melt-compounded into poly(lactic acid) (PLA) with plasticizer. Polymer. 187: 122101. https://doi.org/10.1016/j.polymer.2019.122101.

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    Keywords

    Poly(lactic acid), nucleation, nanocellulose, Avrami kinetics, crystallization

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