Easy alignment and effective nucleation activity of ramie fibers in injection-molded poly(lactic acid) biocomposites

Authors

  • Huan Xu,

    1. Department of Plastics Engineering, College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, 610065, Sichuan, People's Republic of China
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  • Chun-Yan Liu,

    1. Department of Plastics Engineering, College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, 610065, Sichuan, People's Republic of China
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  • Chen Chen,

    1. Analytical and Testing Center, Sichuan University, Chengdu, 610065, Sichuan, People's Republic of China
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  • Benjamin S. Hsiao,

    1. Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400
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  • Gan-Ji Zhong,

    Corresponding author
    1. Department of Plastics Engineering, College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, 610065, Sichuan, People's Republic of China
    • Department of Plastics Engineering, College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, 610065, Sichuan, People's Republic of China
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  • Zhong-Ming Li

    Corresponding author
    1. Department of Plastics Engineering, College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, 610065, Sichuan, People's Republic of China
    • Department of Plastics Engineering, College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, 610065, Sichuan, People's Republic of China
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  • This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley. com

Abstract

The poly(lactic acid) (PLA)/ramie fiber biocomposites were fabricated, which exhibited considerable reinforcement effect comparable to the glass fiber at the same loading. The attempts were made to understand the flow-induced morphology of ramie fibers and PLA crystals in the injection-molded PLA/ramie fiber biocomposites, thus revealing its relationship to biocomposite mechanical properties. The polarized optical microscopy (POM) and two-dimensional wide-angle X-ray diffraction (2D-WAXD) were for the first time used to determine the distribution of nature fibers, which interestingly showed the ramie fibers aligned well along the flow direction over the whole thickness of injection-molded parts, instead of skin-core structure. This easy alignment of ramie fibers during the common processing was ascribed to the intrinsically high flexibility of ramie fibers and strong interfacial interaction between PLA chains and cellulose molecules of ramie fibers. Both 2D-WAXD and differential scanning calorimeter (DSC) measurements suggested that the PLA matrix in its ramie biocomposites had rather high orientation degree and crystallinity, which was attributed to effective heterogeneous nucleation induced by ramie fibers and local shearing field in the vicinity of fiber surface. Remarkable improvement of mechanical and thermo-mechanical properties was achieved for PLA/ramie fiber biocomposites, without sacrifice of toughness and ductility. Addition of 30wt% ramie fibers increased the tensile strength and modulus of PLA/ramie fiber biocomposites from 65.6 and 1468 MPa for pure PLA to 91.3 and 2977 MPa, respectively. These superior mechanical properties were ascribed to easy alignment of ramie fibers, high crystallinity of PLA, and favorable interfacial adhesion as revealed by scanning electron microscopy (SEM) observation and theoretical analysis based on dynamic mechanical analysis (DMA) data. © 2012 Wiley Periodicals, Inc. Biopolymers 97: 825–839, 2012.

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