Thermomechanical properties and water uptake capacity of soy protein‐based bioplastics processed by injection molding

Abstract

The optimization of the processing conditions in the production of soy protein bioplastics by injection molding has been essential in order to develop materials with a great capacity to absorb water while displaying good mechanical properties. Using a 50/50 (wt/wt) soy protein/glycerol mixture, and 40 °C, 500 bar, and 70 °C as reference values for cylinder temperature, injection pressure, and mold temperature, respectively, the effect of those processing parameters over thermomechanical and hydrophilic properties was studied. Processing parameters did not show a great influence over the thermomechanical bending properties within temperatures ranging from −30 to 130 °C, as most samples displayed a similar response, independently of the parameter studied. On the other hand, when studying tensile and hydrophilic properties, the main effect corresponded to the cylinder and mold temperature values, as pressure did not exert a clear influence when increased from 300 to 900 bar. Samples with a lower water uptake were obtained when processed at higher temperature, as a result of crosslinking promotion. Moreover, a greater extensibility was observed when bioplastics are processed at high mold temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43524.

Development of superabsorbent soy protein‐based bioplastic matrices with incorporated zinc for horticulture

“…Thus, the blends were introduced in a MiniJet Piston Molding System II (ThermoHaake, Karlsruhe, Germany) where they were injected through a nozzle into a previously heated mold. The parameters in this stage were selected based on the rheological characterization of the blends and on previous studies to optimize the water uptake capacity of SPI/Gly systems a cylinder and mold temperature of 40 and 70 °C, respectively; an injection pressure of 500 bar (for 20 s), and a post‐injection pressure of 200 bar (for 300 s).…”

“…Soy protein‐based SAB matrices can be manufactured by injection molding, one of the most common techniques for the manufacture of synthetic plastics. This facilitates its implementation on an industrial scale . However, the incorporation of micronutrients generally hinders the processing of these matrices, as it results in a reduction in the strengthening potential of the matrix associated with a corresponding reduction in the protein content …”

“…From all the different proteins studied in the literature related to protein-based SAB matrices (based on pea, 15 egg albumen, 16 crayfish, 17 rice, 18 soy, 19 and whey 20 ), soy protein has proven to be the one with the best absorbent capacity, due to its high glutamic and aspartic acid content, which gives it a good hydrophilic character. 21 Its high lysine content also allows the introduction of some carboxylic groups, improving its hydrophilic character. 22 Soy protein-based SAB matrices can be manufactured by injection molding, one of the most common techniques for the manufacture of synthetic plastics.…”

“…This facilitates its implementation on an industrial scale. 21,23,24 However, the incorporation of micronutrients generally hinders the processing of these matrices, as it results in a reduction in the strengthening potential of the matrix associated with a corresponding reduction in the protein content. 25 The main objective of the present work is therefore the development of suitable soy protein-based matrices with zinc, chelated with 2,2 ′ ,2 ′′ ,2 ′′′ -(ethene-1,2-diyldinitrilo)tetraacetic acid (Zn EDTA), which is a salt that contains the essential micronutrient for plants.…”

Controlled biodegradation of polymers using nanoparticles and its application

“…carbon neutrality. Others are soy-based bioplastics [34], pea protein-based bioplastics [35] and cellulosebased bioplastics [36]. Therefore, the use of bio-or renewable carbon as opposed to petro-or fossil carbon for manufacturing of bio-based plastic reduces the carbon footprint [30,31].…”