Elastoplastic properties of starch-based materials as revealed by microindentation measurements

The elastoplastic properties of injection-molded starch and starch-cement composites were investigated by load-displacement analysis from depth-sensing experiments. The creep behavior under the indenter was studied. Hardness data from the depth-sensing and imaging methods were shown to be in good agree ment. The Young modulus values derived from the compliance method were studied; results are discussed in the light of the various materials used. Finally, the influence of annealing temperature on the microhardness of starch and of the starch-cement composites, processed under a water vapor atmosphere, was investigated. Results reveal a hardening of the materials on thermal treatment. This hardness increase is associated with an equilibrium water content decrease detected within the samples.