Production and characterization of microfibrillated cellulose-reinforced thermoplastic starch composites

In this study thermoplastic starch (TPS) matrix-based microfibrillated cellulose (MFC) reinforced microcomposites were prepared via extrusion compounding in one-step. Starch was plasticized with a combination of glycerol and water. The native starch/glycerol and the plasticized starch/water ratios were set for 4/1 and 6/1, respectively. Two different MFC types (of varying mean length and diameter) were incorporated up to 20 wt % in the plasticizer-containing premix prior to its compounding in a twin-screw extruder. The mechanical properties of the TPS biocomposites were markedly enhanced by the introduction of MFC. The yield strength was improved by similar to 50%, whereas the stiffness by similar to 250% upon adding 20 wt % MFC compared to the parent TPS. Dynamic mechanical analysis (DMA) revealed that the reinforcing effect of the MFC was more prominent in the starch-than in the glycerol (plasticizer)-rich phase of the TPS. The mean length and diameter of the MFCs, yielding similar aspect ratio values lying below the estimated critical one, influenced the mechanical, thermal, and thermo-mechanical properties marginally. (C) 2015 Wiley Periodicals, Inc.