Jeudi 3 Septembre 2009
par- 19 juillet 2010
Prof. Críspulo Gallegos
Departamento de Ingeniería Química. Universidad de Huelva. Campus de “El Carmen“. 21071 Huelva, Spain.
PROCESSING AND RHEOLOGY OF CONTROLLED-RELEASE PROTEIN-BASED BIOPLASTICS
Population and economy growth worldwide have caused an enormous increase in waste production. To minimize this problem, some alternatives are being studied, such as, for instance, recycling of plastic materials and substitution of conventional plastics by biodegradable polymers. Biopolymer materials derived from renewable agricultural resources have centred a remarkable interest in the last few years. In this sense, many different thermoplastic biopolymers have been developed and commercially produced using current levels of technology. The main renewable sources of biopolymers are proteins, polysaccharides and lipids. Proteins are thermoplastic heteropolymers of both polar and nonpolar amino acids that are able to form numerous intermolecular linkages, and undergo different interactions, yielding a wide range of potential functional properties. Moreover, plant proteins are inexpensive, renewable and abundant raw materials. A way of processing protein-based biomaterials is the mechanical method, or thermoplastic processing, which consists of mixing proteins and plasticizer to obtain a dough-like material. In thermo-plastic material processing, the specific mechanical energy, shear impact, pressure, plasticizer, time, and temperature are examples of important parameters, which determine the extent of conformational changes, aggregation, and chemical cross-linking that occur during processing. Bioplastic applications include matrices for enzyme immobilization, matrices for controlled-release devices, etc. It is possible to use the advantage of their low solubility in water, as well as their enormous water up-taking (swelling), in order to develop further applications, such as water absorbent materials. Thus, they are mainly used as absorbents in healthcare, agriculture and horticulture applications. The aim of this presentation is to introduce new controlled-release bioplastics based on glycerol, water, wheat gluten and an “active agent”. An overview on the effect that formulation, processing, and further thermal treatments exert on the thermo-mechanical properties, physico-chemical characteristics and rheological behaviour of the bioplastics obtained will be presented.
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