Effect of plasticizer on the structure of biodagradable starch/clay nanocomposites: thermal, water sorption and oxygen barrier properties

International audienceIn this study, we investigated nanocomposites based on a plasticized natural biodegradable matrix. The polymer used was a natural potato starch, and the plasticizers were glycerol and a urea/ethanolamine mixture. A natural and an organically modified montmorillonite were studied. Two series of films containing 6 wt % nanoclays were prepared by a solution/cast process: the first series was based on neat starch, and the second one was based on 20 wt % plasticized starch. For all matrices, a mixture of intercalated and exfoliated structures was formed by the addition of pristine montmorillonite, whereas an aggregate structure was obtained with organoclay. The thermal stability was not significantly influenced by the addition of clays. Water sorption was examined as a function of the matrix and clay hydrophilicity. The significant reduction of oxygen permeability obtained with natural montmorillonite was related to the high dispersion state of this clay. For urea-ethanolamine composites, specific compatibilizer/clay interactions led to an improvement again in the barrier propertie

Starch thermal processing: technologies at laboratory and semi-industrial scales

Multilevel structure and multiphase thermal transition of starch make its processing much more complex than that of synthetic polymers. This chapter discusses the unique structure and phase transition of native starch, as well as rheological properties of starch during thermal processing. The techniques used to study these characteristics are described. However, although starch can be processed using the conventional techniques designed for synthetic polymers, these techniques should be adapted along with optimized operational conditions and formulations. Regarding this, this chapter summarizes various processing techniques at laboratory and semi-industrial scales such as solution casting, extrusion, injection and compression moldings, as well as other innovative methods such as reactive extrusion. In particular, the most important aspects of starch processing pertaining to the use of plasticizers, blending with other polymers or ingredients, and orientation are discussed. Accordingly, native starch can be processed into different forms of plastic product such as films/sheets, foams and shaped articles for food packaging and other niche applications