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Keywords:

  • biopolymers;
  • clay;
  • crosslinking;
  • mechanical properties;
  • nanocomposites

Abstract

The objectives of this study were to investigate the effect of epoxide content (24–88 mol %) on the mechanical properties and characteristics of epoxidized soybean oil (ESO) and to compare the mechanical properties of ESO–organoclay nanocomposites with different epoxide contents (40 and 100 mol %). ESO was synthesized by in situ epoxidation with acetic acid and hydrogen peroxide. We prepared ESO bioplastic sheets from ESO by curing with methyltetrahydrophthalic anhydride and 1-methylimidazole. The tensile properties and tear resistance of the synthesized bioplastic (ESO40, where the number indicates the molar percentage of epoxidation) were investigated and compared with ESO bioplastic sheets prepared from commercial ESO with 100 mol % epoxidation (ESO100). The tensile modulus, tensile strength, tensile toughness, and tear strength of the ESO bioplastics increased with increasing epoxide content, whereas the elongation at break of the ESO100 bioplastic was lowest. No trend was observed in the bioplastics prepared from ESO24–ESO88. Dynamic mechanical thermal analysis showed increases in the storage modulus and glass-transition temperature as the epoxide content was increased. Thermal degradation also increased with increasing epoxide content. The crosslink density and chain flexibility controlled the mechanical properties and characteristics of the ESO bioplastics. ESO–organoclay nanocomposites were prepared by in situ intercalative polymerization. The addition of organoclay increased the mechanical properties of the ESO bioplastics. The effect of organoclay content (1–8 wt %) on the mechanical properties was similar to the effect of the epoxide content. The sESO100 nanocomposite showed a higher modulus but lower tensile strength and elongation at break than the ESO40 nanocomposite. Intercalation of the organoclay in the ESO nanocomposites was observed by transmission electron microscopy and X-ray diffractometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009