Effectiveness of thermo-compression for manufacturing native starch bulk materials
In this study, thermo-compression molding was used to fabricate bulk materials from native starch powder. The objective was to determine the process parameters that enabled the welding of starch granules while preserving their crystallinity. The effects of forming parameters such as temperature, compression stress, and water content on the microstructural and mechanical properties of the starch samples were studied. For the optimal forming conditions, good compaction and cohesion of starch granules were obtained, while successfully preserving their native crystalline structure. The flexural Young’s modulus of the best samples reached an average value of 3 GPa and the flexural strength reached 10 MPa. However, these materials also exhibited unwanted cracks. The potential origin of these defects was associated to the heterogeneous distribution of water during processing as well as thermal shrinkage, moisture uptake, and viscoelastic recovery that occurred after the mold ejection.
KeywordsStarch Welding Compaction Compressive Stress Starch Granule
The authors gratefully acknowledge Institut Carnot PolyNat for funding this study. Besides, they would like to thank S. Rolland du Roscoat, P. Charrier, B. Khelifi, D. Curtil, R. Passas, C. Sillard, and S. Dufreney for their technical support, as well as R. Léger from Centre des Matériaux des Mines d’Alès (C2MA) at École des mines d’Alès for assistance with pycnometer experiments. The LGP2 and 3SR laboratories are part of LabEx Tec 21 (Investissements d’Avenir—Grant Agreement No. ANR-11-LABX-0030).
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