Abstract
Antimicrobial active films based on poly (lactic acid) (PLA) were prepared with nano-silver (nano-Ag) and nano-zinc oxide (nano-ZnO) using a solvent volatilizing method. The films were characterized for mechanical, structural, thermal, physical and antimicrobial properties. Scanning electron microscopy (SEM) images characterized the fracture morphology of the films with different contents of nano-Ag and nano-ZnO. The addition of nanoparticles into the pure PLA film decreased the tensile strength and elasticity modulus and increased the elongation of breaks—in other words, the flexibility and extensibility of these composites improved. According to the results of differential scanning calorimetry (DSC), the glass transition temperature of the PLA nano-composite films decreased, and the crystallinity of these films increased; a similar result was apparent from X-ray diffraction (XRD) analysis. The water vapor permeability (WVP) and opacity of the PLA nano-composite films augmented compared with pure PLA film. Incorporation of nanoparticles to the PLA films significantly improved the antimicrobial activity to inhibit the growth of Escherichia coli. The results indicated that PLA films with nanoparticles could be considered a potential environmental-friendly packaging material.
Highlights
In last few decades, plastic bags made of polyethylene (PE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) have become common in daily life [1].These polymers are non-biodegradable and use petroleum as their raw material, and the environment can be contaminated with these bags [2]
The structures of pure PLA and PLA nano-composite films were analyzed by X-ray diffraction
The Xc could be improved by annealing according to the requirements of the biodegradation rate and the mechanical properties for the applications. All of these results suggested that the nanoparticles could promote crystallization of PLA, including cold crystallization and re-crystallization
Summary
Plastic bags made of polyethylene (PE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) have become common in daily life [1] These polymers are non-biodegradable and use petroleum as their raw material, and the environment can be contaminated with these bags [2]. PLA has other advantages, like moderate mechanical properties, transparency, commercial availability and low price [5,6,7,8]. As a consequence, these advantages give PLA the best potential for packaging and medical applications [6,8]. We tried to prepare PLA composite films with nano-silver (nano-Ag) and nano-zinc oxide (nano-ZnO)
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