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Bionanocomposites (BNCs) based on thermoplastic zein (TPZ) and unmodified sodium montmorillonite (MMT), at 1, 2.5, 5, and 10 wt % loading, were prepared by using an internal mixer. The nanocomposites were characterized by using the following analytical methods: small‐angle and wide‐angle X‐ray diffraction, thermogravimetric, dynamic‐mechanical and mechanical analyses. Results evidenced that the efficient dispersion of the inorganic reinforcement, as proved by X‐ray diffraction, allowed for an effective improvement of thermal and mechanical properties of the BNCs with respect to the neat TPZ. In particular, a significant increase of the storage modulus in the whole temperature range was observed in dynamic‐mechanical experiments. A dramatic increase of mechanical properties has also been observed, with Young's modulus increasing from 296 MPa for neat TPZ to 1205 MPa at 5 wt % and to 1478 at 10 wt % of MMT. The observed dependencies are explained by means of three concurring mechanisms: (i) the stiffening by exfoliated MMT platelets, (ii) the development of strong interactions between the nanoparticles and the protein macromolecules, promoted by the low‐molecular weight plasticizer, (iii) the occurrence of possible plasticizer sequestration by MMT and the corresponding reduction of plasticizing effect on the protein. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

The aim of this study was to utilize zein, a protein from corn, to develop bioplastic formulations in combination with reactive additives based on ligninic compounds and to investigate the effects of these highly interactive additives on the foamability of zein. In particular, different amounts of alkaline lignin and sodium lignosulfonate were added to zein powder and poly(ethylene glycol) through melt mixing to achieve thermoplastic bio-polymers, which were subsequently foamed in a batch process, with a mixture of CO2 and N2 as blowing agent, in the temperature range 50–60C. The materials before foaming were characterized by X-ray and Fourier transform infrared analysis to highlight the physico-chemical interactions and the eventual destructuration of the protein secondary structure. After foaming, density measurements, scanning electron microscopy and image analysis have been used in order to evaluate the porosity and the pore size distribution of the microstructure of the foams and to determine the effect of the ligninic compounds on the foamability of the bioplastic

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