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Recent environmental problems and societal concerns associated with the disposal of petroleum based plastics throughout the world have triggered renewed efforts to develop new biodegradable products compatible with our environment. This article describes the preparation, characterization and biodegradation study of poly(lactic acid)/layered double hydroxide (PLA/LDH) nanocomposites from PLA and stearate-Zn3Al LDH. A solution casting method was used to prepare PLA/stearate-Zn3Al LDH nanocomposites. The anionic clay Zn3Al LDH was firstly prepared by co-precipitation method from a nitrate salt solution at pH 7.0 and then modified by stearate anions through an ion exchange reaction. This modification increased the basal spacing of the synthetic clay from 8.83 Å to 40.10 Å. The morphology and properties of the prepared PLA/stearate-Zn3Al LDH nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), thermogravimetric analysis (TGA), tensile tests as well as biodegradation studies. From the XRD analysis and TEM observation, the stearate-Zn3Al LDH lost its ordered stacking-structure and was greatly exfoliated in the PLA matrix. Tensile test results of PLA/stearate-Zn3Al LDH nanocomposites showed that the presence of around 1.0-3.0 wt % of the stearate-Zn3Al LDH in the PLA drastically improved its elongation at break. The biodegradation studies demonstrated a significant biodegradation rate improvement of PLA in the presence of stearate-Zn3Al LDH nanolayers. This effect can be caused by the catalytic role of the stearate groups in the biodegradation mechanism leading to much faster disintegration of nanocomposites than pure PLA. [ABSTRACT FROM AUTHOR]

Anionic clay Mg-Al Layered double hydroxide (Mg-Al LDHs) of Mg/Al-NO3- with M2+:M3+ (3:1) ratio was synthesized by co-precipitation method from nitrate salt solutions were used with continuous agitation at constant pH 9. Beside, modification of nitrate anions by stearate anions between the LDH layers had carried out through ion exchange reaction. Polyhydroxybutyrate (PHB)/Polycaprolactone (PCL)/stearate Mg-Al Layered Double Hydroxide (LDH) nanocomposites were prepared via solution casting intercalation method. FT-IR spectra showed the presence of carboxylic acid (COOH) group indicates that stearate anions were successfully replacing the nitrate anions in the interlayer Mg-Al LDH. The XRD results showed that increasing basal spacing from 8.66 to 32.97 Å in modified stearate Mg-Al LDH. Additional of 1.0 wt % stearate Mg-Al LDH resulting higher basal spacing where polymer chain intercalated into interlayer LDH and TEM results revealed that the 1.0 wt % stearate Mg-Al LDH layers are homogeneously distributed in the PHB/PCL polymer blends matrix. TGA characterization proven that 80PHB/20PCL/1stearate Mg-Al LDH has lower weight loss and higher thermal stability. Enhancement in 300% elongation at break and 66% tensile strength in the presence of 1.0 wt % of the stearate Mg-Al LDH as compare with PHB/PCL blends. Scanning electron microscopy (SEM) proved that clay improves compatibility between polymer matrix and the best ratio 80PHB/20PCL/1stearate Mg-Al LDH surface was well dispersed and stretched before it breaks. [ABSTRACT FROM AUTHOR]

Poly-3-hydroxybutyrate/Poly(butyleneadipate-co-terephthalate)/layered double hydroxide (PHB/PBAT/LDH) nanocomposites were prepared from PHB/PBAT blend and stearate Zn3Al LDH via a solution casting method in this study. By using co-precipitation method, the pristine Zn3Al LDH was prepared from nitrate salts solution at pH 7 and then modified by stearate anions through an ion exchange reaction. This modification increased the basal spacing of the LDH from 8.77 to 24.94 Å. The stearate Zn3Al LDH infrared spectrum showed the presence of stearate ions in the synthesized Zn3Al LDH. Mechanical properties of the nanocomposites with 2 wt% stearate Zn3Al LDH content show 56 wt% improvements in elongation at break compared to those of the blend. [ABSTRACT FROM AUTHOR]