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The Influence of Biocomposite Processing and Composition on Natural Fiber Length, Dispersion and Orientation



Author(s)

Peltola Heidi¹, Madsen Bo², Joffe Roberts ³ and Nättinen Kalle¹

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DOI:10.17265/2161-6213/2011.07.008

1. Vtt Technical Research Centre of Finland, 33101 Tampere, Finland
2. Technical University of Denmark, Risø National Laboratory for Sustainable Energy, Materials Research Division, Roskilde DK-4000, Denmark
3. Department of Applied Physics and Mechanical Engineering, Luleå University of Technology, Luleå SE-97187, Sweden

In the study, the effect of process steps, melt viscosity and fiber type on the fiber length of biocomposites from triethyl citrate plasticized starch acetate and natural fibers was investigated. Composites were prepared by melt processing (compounding and injection molding). The lengths of fully processed fibers were determined by dissolving the starch acetate matrix and measuring the length of the remaining fibers by optical microscopy and image analysis. A clear reductive effect of the pelletising and melt processing on the fiber length was noticed. Also a reduction of fiber length along the increasing fiber content and the decreasing plasticizer content was detected. This reduction was originated from the increasing shear forces during compounding, which again depended on the increased viscosity of the material. When comparing the fully processed hemp and flax fibers, hemp fibers remained longer and fibrillated more than flax fibers, leading to higher aspect ratio. Thus, the reinforcement efficiency of hemp fibers by the processing was improved, on the contrary to the reduced reinforcement efficiency of flax fibers. In addition, the analysis of fiber dispersion and orientation showed a good dispersion of fibers in the matrix, and a predominant orientation of the fibers in the melt flow direction.

Starch acetate, natural fiber composite, fiber length, fiber distribution.