Plasticized starch/tunicin whiskers nanocomposite materials.: 2.: Mechanical behavior

In a previous work [Macromolecules 2000, 33, 8344], nanocomposite materials were obtained using glycerol plasticized starch as the matrix and a colloidal suspension of tunicin--an animal cellulose-whiskers as the reinforcing phase. The mechanical behavior of resulting films was characterized in both the linear and the nonlinear range. The effects of the filler and water contents were evaluated, and the results were discussed on the basis of the knowledge of the structural morphology reported in the first part of the paper. The reinforcing effect of tunicin whiskers strongly depended on the ability of cellulose filler to form a rigid network, resulting from strong interactions between whiskers such as hydrogen bonds, and therefore on the moisture content. It was shown that increasing water content induced the crystallization of amylopectin chains and the accumulation of plasticizer in the cellulose/amylopectin interfacial zone. Both phenomena strongly interfere with hydrogen-bonding forces likely to hold the percolating tunicin whiskers network together.