Strategies to Produce Thermoplastic Starch-Zein Blends: Effect on Compatibilization

Different strategies to produce thermoplastic materials using starch and zein were studied, aiming to investigate their effect on the compatibility of starch and zein. Research strategies comprised the use of two different plasticizers for starch, two different compatibilizing agents, and two blending procedures. The plasticizers were mixtures of sorbitol and glycerol (SG) or urea and formamide (UF). UF and maleated starch (MS) were used as compatibilizing agents. The blending procedures included: (1) thermoextruding starch and zein as premixed powder materials (TP[Mix]) and (2) coextruding the biopolymers previously thermoplasticized with suitable plasticizers. As observed by the tensile tests, scanning electronic microscopy, and dynamic mechanical analysis, segregation of phases occurred at different extents in all the starch–zein blends. Materials made with MS through the TP[Mix] procedure presented the most severe phases segregation, while the materials made with UF showed higher compatibility between starch and zein. Fourier Transform Infrared Spectroscopy (FTIR) suggests that increased zein content leads to a lower molecular order, which was ascribed to diminished molecular entanglement. Thermogravimetric analysis and FTIR analysis showed that the chemical interaction between starch and zein occurred more extensively in slabs made with UF than those made with MS. In addition, foamability was evaluated for the selected materials using supercritical CO2. Neat thermoplasticized starch plasticized with UF and themoplasticized zein with polyethylene-glycol 400 showed good suitability to be foamed, producing foams with porosities above 85 %. Starch plasticized with SG and starch–zein blends yielded compact structures with low porosity values after foaming

Thermoplastic processing of blue maize and white sorghum flours to produce bioplastics

In this study, we evaluated the feasibility of producing bioplastics from blue maize (BM) and white sorghum (WS) flours by thermoplasticization using sorbitol and glycerol as plasticizers and by using extrusion and compression molding. The analyzed variables were screw speed rotation (50–70 rpm), extrusion temperature (100–140 °C), number of extrusion passes (1 or 2), and chemical modification of the flours with maleic anhydride. Mechanical characterization revealed a major effect of the extrusion temperature among the processing variables studied, and the microstructure and slab color varied sig- nificantly with temperature. Chemical modification also had a major effect on the properties of the produced materials. Slabs made with chemically modified flours showed increases in their mechanical properties compared to their native counterparts. Consistently, scanning electronic microscopy revealed a more uniform micro- structure in slabs made with chemically modified flours, and dynamic mechanical analysis indicated a better matrix- plasticizer interaction in these slabs when compared to slabs made with native flours. The BM and WS flours were determined to be suitable raw materials for producing thermoplastic materials

Supercritical CO2 foaming of thermoplastic materials derived from maize: proof-of concept use in mammalian cell culture applications

Foams are high porosity and low density materials. In nature, they are a common architec- ture. Some of their relevant technological applications include heat and sound insulation, lightweight materials, and tissue engineering scaffolds. Foams derived from natural poly- mers are particularly attractive for tissue culture due to their biodegradability and bio-com- patibility. Here, the foaming potential of an extensive list of materials was assayed, including slabs elaborated from whole flour, the starch component only, or the protein frac- tion only of maize seeds