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Title: Benefits of low kenaf loading in biobased composites of Poly (L-lactide) and kenaf fiber

Author
item OGBOMO, SUNNY - UNIV. NORTH TEXAS
item CHAPMAN, KENT - UNIV. NORTH TEXAS
item Webber Iii, Charles
item BLEDSOE, ROBERT - INTERNATIONAL KENAF ASSOC
item D'SOUZA, NANDIKA - UNIV. NORTH TEXAS

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2008
Publication Date: 1/30/2009
Citation: Ogbomo, S.M., Chapman, K.D., Webber III, C.L., Bledsoe, R.E., D'Souza, N.A. 2009. Benefits of low kenaf loading in biobased composites of Poly (L-Lactide) and kenaf fiber. Journal of Applied Polymer Science. 112:1294-1301.

Interpretive Summary: The need to replace fossil-based materials has led to increased interest in polymer composites derived from biological sources, specifically those containing natural fibers. Fibers from bark of kenaf stems (Hibiscus cannabinus L.), a warm-season herbaceous annual plant, were dispersed into Poly-L-Lactide (PLLA) matrix by heating and molding to form composites. Low fiber fractions (1-5%) were used. The composites had a slightly lower thermal stability. Kenaf fibers influenced crystallization of the PLLA. The type of matrix and fiber affected results. The feasibility of successfully fabricating PLLA-kenaf natural fiber composites is possible with a 1-5% kenaf content. Increases in stiffness and crystallization rates compared well compared to 10, 20, and 30% kenaf containing composites reported in previous research. Addition of kenaf to PLLA increased storage and thermal properties, while improving crystallization rate even at low kenaf levels. There was good fiber wetting between the PLLA and kenaf. These results are significant as comparisons to conventional fillers with natural filler fibers are made. These results may lead to increased movement to, or development of, safer, green, environmentally friendlier, and cheaper materials with a resulting improvement in mechanical properties for use throughout the manufacturing industries.

Technical Abstract: Bast fibers from stems of kenaf (Hibiscus cannabinus L.), a warm-season herbaceous annual plant, were dispersed into Poly-L-Lactide (PLLA) matrix by melt mixing followed by compression molding. Low fiber fractions (1-5%) were investigated. The composites showed a slight lowering of thermal stability when evaluated by Thermogravimentric analysis (TGA). X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC) indicated an influence of kenaf on crystallization of the PLLA. Attenuated Total Reflectance-Fourier transfer infrared spectroscopy (ATR-FTIR) showed increased matrix-fiber interaction. Increased interaction resulted in good fiber-matrix adhesion, as revealed by Scanning Electron Microscopy. The fiber dispersion in the polymer matrix was established by polarized optical microscopy. The combination of dispersion, interaction, and crystallinity enabled an increase in mechanical properties in the composite, which scaled with concentration. These results established the feasibility of successfully fabricating PLLA-kenaf natural fiber composites with very low kenaf loading (1-5%). The enhancement in stiffness and crystallization rates compared well to 10, 20, 30% kenaf containing composites reported in the literature. The addition of kenaf to PLLA increased the storage modulus and thermal properties, while improving the crystallization rate at low kenaf loading. An interaction between PLLA and kenaf was established by FTIR. The interaction enabled good fiber wetting by the PLLA as indicated by SEM. These results are significant as we compare the conventional-based filler with natural-based filler fibers. We envision an increased movement to, or development of safer, green, environmentally friendlier, and cheaper materials, with a resulting improvement in mechanical properties.