Effect of Alkali Treatment on Structure and Properties of High Amylose Corn Starch Film

Alkali treatment is used for melt extrusion film formation with corn starch, but optimal conditions for this procedure are still unknown. In this study, the changes in properties and structure of high amylose corn starch (70%) films with different concentrations of sodium hydroxide (NaOH), prepared by melting extrusion, were investigated. With increasing sodium hydroxide concentrations, the tensile strength of the high-amylose starch film decreased gradually, while the elongation at break increased. The tensile strength of the high amylose starch (HAS) film with 2% NaOH-treatment was 10.03 MPa and its elongation at break was 40%. A 2% NaOH-treatment promoted the orderly rearrangement of starch molecules and formed an Eh-type crystal structure, which enlarged the spacing of the single helix structure, increased the molecular mobility of the starch, and slowed down the process of recrystallization; a 10% NaOH-treatment oxidized the hydroxyl groups of the high amylose corn starch during extrusion, formed a poly-carbonyl structure, and initiated the degradation and cross-linking of starch molecule chains

Effects of Organic Modification of Montmorillonite on the Properties of Hydroxypropyl Di-Starch Phosphate Films Prepared by Extrusion Blowing

The knowledge gained from starch-nanocomposite-film research has not been fully applied commercially because of the lack of appropriate industrial processing techniques for nanofillers and starch films. Three organically modified montmorillonites (OMMTs) were prepared using a semidry kneading method. The effects of the OMMTs on the structures and properties of starch nanocomposite films, prepared by extrusion blowing, were investigated. The X-ray diffraction (XRD) analysis results revealed that the OMMTs with various quaternary ammonium salts possessed differing layer structures and d-space values. The results of the XRD and Fourier-transform infrared spectroscopy (FT-IR) showed that the starch–OMMT interaction resulted in a structural change, namely the starch–OMMT films possessed a balanced exfoliated and intercalated nanostructure, while the starch–MMT film possessed an exfoliated nanostructure with non-intercalated montmorillonite (MMT). The results of the solid-state nuclear magnetic resonance (NMR) analysis suggested that the starch-OMMT nanocomposite possessed comparatively large quantities of single-helix structures and micro-ordered amorphous regions. The starch–OMMT films exhibited good tensile strength (TS) (maximum of 6.09 MPa) and water barrier properties (minimum of 3.48 × 10−10 g·m·m−2·s−1·Pa−1). This study indicates that the addition of OMMTs is a promising strategy to improve the properties of starch films

Thermal stability of levopimaric acid and its oxidation products

Abstract Biofuels are renewable alternatives to fossil fuels. Levopimaric acid‒base biofuels have attracted increasing attention. However, their stability remains a critical issue in practice. Thus, there is a strong impetus to evaluate the thermal stability of levopimaric acid. Through thermogravimetry (TG) and a custom-designed mini closed pressure vessel test (MCPVT) operating under isothermal and stepped temperature conditions, we investigated thermal oxidation characteristics of levopimaric acid under oxygen atmosphere. Thin-layer chromatography (TLC) and iodimetry were used to measure the hydrogen peroxides generated by levopimaric acid oxidation. A high pressure differential scanning calorimeter (HPDSC) was used to assess hydroperoxide thermal decomposition characteristics. Gas chromatography-mass spectrometry (GC-MS) was used to characterize the oxidation products. The thermal decomposition kinetics of levopimaric acid were thus elucidated, and a high peroxide value was detected in the levopimaric acid. The decomposition heat (QDSC) and exothermic onset temperature (Tonset) of hydroperoxides were 338.75 J g−1 and 375.37 K, respectively. Finally, levopimaric acid underwent a second-stage oxidation process at its melt point (423.15 K), resulting in complex oxidation products. Thermal oxidation of levopimaric acid could yield potential thermal hazards, indicating that antioxidants must be added during levopimaric acid application to protect against such hazardous effects