Novel ecological starch-based biocomposite films reinforced with acetate-intercalated layered double hydroxides: Enhanced optical, dielectric, and mechanical properties

Abstract

In this study, biocomposite films based on thermoplastic starch (TPS) reinforced up to 5 wt% with acetate intercalated Mg-Al layered double hydroxide (LDH-Ac), were synthesized by the solution casting method, while LDH-Ac was synthesized by coprecipitation at a constant pH. The use of analytical techniques, including X-ray diffraction, infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and energy-dispersive X-ray analysis, provide substantial evidence for the homogeneous dispersion of the reinforcing agent within the biocomposite films. It was found that with increasing LDH-Ac content, the biocomposite films demonstrated a good resistance against the water solubility and showed increasing their biodegradability. The enhancement of their optical properties was evidenced through the decrease of the optical gap energy and transmission light and the increase of the light absorption, opacity, refractive index, Urbach energy, optical conductivity and optical dielectric constant. Furthermore, the increase in the LDH-Ac content resulted an improvement of the dielectric properties, as evidenced by a reduction in the dielectric loss tangent. This increase also led to an enhancement of the mechanical properties, as demonstrated by an increase in the tensile strength and Young’s modulus. The optical, dielectric and mechanical performances of the biocomposite films are likely due to the synergy generated by the interaction between the functional groups of TPS (carboxyl and hydroxyl) and species containing LDH-Ac (metals, hydroxyl, acetate, and water molecules). The results of the study suggest that thermoplastic starch reinforced with acetate intercalated Mg-Al layered double hydroxide-based biocomposite films have potential applications in packaging, optoelectronics and dielectric energy storage.