Properties of compression-molded, acetylated soy protein films

The demand for biodegradable polymers produced from renewable natural resources continues to grow as environmental concerns increase. The objective of this study is to examine how acetylated soy protein isolate performed as a thermoplastic and how the properties of films made from it are affected by composition and morphology. SUPRO (R) 620 and 660 were modified and acetylated to produce SY7 and SY23 thermoplastic films. These films were formed under various compression-molding conditions to form films of two thicknesses and relative molecular weights. No plasticizer was used in forming these films. Molded films were then evaluated for total and volatile solids, nitrogen content, chemical oxygen demand, flow rate, solubility, X-ray diffraction, H-1 and C-13 NMR, differential scanning calorimetry, infrared analysis, tensile properties, oxygen and water vapor permeability. A comparison of melt flow index values, nitrogen content, total solids, volatile solids, and chemical oxygen demand demonstrated no statistical differences between films, but significant differences from SUPRO (R) 620 the base material used to form SY7. The SY7 films had lower solubility, lower 'wet' tensile strength, and higher oxygen permeability than the SY23 films. Both the SY7 and SY23 films formed at higher compression molding temperatures had higher tensile strengths, increased 'wet' elongation, and lower water vapor permeability than the films formed at lower compression molding temperatures. X-Ray diffraction,H-1 and C-13 NMR, differential scanning calorimetry, and infrared analysis exhibited slight or no differences between the SY7 and SY23 films. Compression molded thermoplastics produced from acetylated SUPRO (R) 620 and 660 appear similar and a possible commercial thermoplastic. (C) 2001 Elsevier Science B.V. All rights reserved.