Abstract
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.
Highlights
Nowadays a great amount of various petroleum based polymers such as polyolefins, poly(vinyl chloride) and polystyrene are used
The objective of our research is to investigate the influence of the stearate-Zn3Al layered double hydroxide (LDH) nanolayers on the tensile properties and the biodegradability of poly lactic acid (PLA)
It is apparent that both Zn3Al LDH and stearate-Zn3Al LDH are crystalline in nature with a well-defined layered structure
Summary
Nowadays a great amount of various petroleum based polymers such as polyolefins, poly(vinyl chloride) and polystyrene are used. It is estimated that their production exceeds 108 t/a [1]. Since these polymers are highly stable towards most environmental conditions, their consumption and discarding into the environment are major contributions to non-degradable wastes. Recycling is an environmentally attractive solution, only a minor portion of plastics is recycled, and most of these wastes end up in municipal burial sites [2]. Satisfactory landfill sites are limited and disposal of these wastes in incineration leads to the production of toxic or noxious products that contribute to global pollution. It seems that the best solution to overcome these problems is the development of biodegradable polymers or green polymeric materials [3,4]
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