Plasticized starch/tunicin whiskers nanocomposite materials. 2. Mechanicalbehavior

In a previous work [Macromolecules 2000, 33, 8344], nanocomposite materials were obtained using glycerol plasticized starch as the matrix and a colloi dal 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 co ntents were evaluated, and the results were discussed on the basis of the k nowledge of the structural morphology reported in the first part of the pap er. The reinforcing effect of tunicin whiskers strongly depended on the abi lity of cellulose filler to form a rigid network, resulting from strong int eractions between whiskers such as hydrogen bonds, and therefore on the moi sture content. It was shown that increasing water content induced the cryst allization 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 whisker s network together.