Biodegradable soy protein–polyester blends by reactive extrusion process

Abstract

Blends of soy protein concentrate and biodegradable polyester (Eastar Bio Copolyester, EPE) were prepared by using glycerol as a compatibilizing agent. Good miscibility was obtained only when the soy protein was initially combined with glycerol under high shear and at elevated temperatures in an extruder. Under these conditions, partial denaturing of the soy protein led to specific interactions between functional groups of the protein with the glycerol. The extrusion conditions and appropriate screw configuration were the critical factors affecting the reactivity of the protein and hence, the properties of the blends. Screws with large kneading blocks that produced high shear mixing were preferred and led to thermoplastic blends characterized by high elongation and high tensile strength. The morphology of these soy protein/polyester blends was studied by using environmental scanning electron microscopy (ESEM) and indicated good wetting of the soy protein particles within the polyester matrix. The thermal properties were studied by differential scanning calorimetry (DSC) and showed a lower degree of crystallinity and a continuous depression of the melting point of the polyester as the concentration of protein was increased. The possibility of using soy protein concentrate instead of the more expensive (higher purity) soy protein isolate in the preparation of biodegradable resins should lead to new commercial opportunities based on renewable, agricultural byproducts.

Facile exfoliation of rectorite nanoplatelets in soy protein matrix and reinforced bionanocomposites thereof

“…The resultant dark-gray viscous solutions were freeze-dried for 48 h to obtain a series of gray nanocomposite powders, which kept the original complex state in solution. According to the adding REC contents in solid powders of 0, 4,8,12,16,20, and 24 wt %, the nanocomposite powders obtained were coded as SR-0-P, SR-4-P, SR-8-P, SR-12-P, SR-16-P, SR-20-P, and SR-24-P, respectively. The nanocomposite powders were conditioned in a desiccator with silica gel as desiccant for 1 week at room temperature before characterization.…”

“…However, in the plasticization process of soy protein basedplastics to overcome brittleness and poor processablity, 18 it was put forward how to settle the significant decrease of its tensile strength. As a result, blending with other biodegradable polymers was extensively applied, and some candidates, such as polyphosphate, 19 polyester, 20 waterborne polyurethane, 21 polylactic acid, 22 chitin 23 and its whisker, 24 and so on, showed obvious reinforcing effects. In our previous practice, 25,26 the industrial lignins of different types were introduced, and the further improvements were realized by the reinforcement of cellulose 27 and compatibilization of reactive small molecule.…”

Structure and mechanical properties of soy protein materials plasticized by Thiodiglycol

“…[2][3][4][5] Among biopolymers, soy proteins have been considered for potential replacement of synthetic plastics because they can be converted into thermoplastics by solution casting, compression molding, or extrusion. 6,7 They can also be converted into plastics with reduced water vapor permeability at ultrahigh pressures. 8 Soy proteins have environmental benefits, but they often lack mechanical strength and water resistance properties.…”

Morphology and Properties of Soy Protein and Polylactide Blends

“…4 SP plasticizing conditions also showed a significant influence on the compatibility between SP and polyester. 11 Other SP plastics, such as SP/ PU, 12,13 SP/lignin, 14 and SP/chitin, 15,16 have also been studied.…”