A first insight on composites of thermoplastic starch and kaolin

In this work we have studied the utilization of kaolin as filler reinforcement for thermoplastic starch in order to improve its mechanical properties. The composites were prepared with regular cornstarch plasticized with glycerin and reinforced with hydrated kaolin. All the components were pre-mixed and processed in an intensive batch mixer at 170 degreesC. Compounds with 0, 10, 20, 30. 40, 50 and 60 phr - parts of kaolin per hundred parts of thermoplastized starch - were prepared. The mechanical tests were performed from dumb-bell shaped specimens conditioned in ambient for 14 days. The material were also evaluated by DSC, TGA analysis and water sorption experiments. The composite filled with 50 phr kaolin showed an increase in the tensile strength from 5 to 7.5 MPa. The modulus of elasticity increased from 120 to 290 MPa and the tensile strain at break decreased from 30 to 14%. Scanning Electron Microscope of fractured surface revealed the occurrence of strong bonding between kaolin and the matrix. Besides the good mechanical properties, the utilization of these clays leads to an increase in the water resistance of thermoplastic starch compounds also. (C) 2001 Elsevier Science Ltd. All rights reserved.