In this study, biodegradable nanocomposite film composed of pullulan -whey protein isolate (WPI) -montmorillonite (MMT) were developed and characterized as a function of incorporating various amounts of MMT nanoparticles (0, 1, 3 and 5 % wt). Results showed that the watervapor permeability, moisture content, moisture absorption and water solubility decreased when the nano-MMT content was increased. Tensile strength improved and elongation at break simultaneously decreased with increasing MMT content. The glass transition temperature (T g (and melting-point temperature (T m ) increased with increasing nano-MMT content. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis revealed uniform distribution of MMT into the polymer matrix. Atomic force microscopy (AFM) showed enhancement of films' roughness with increasing MMT content.
Nowadays, researchers have attracted to substitute petroleum-based materials by biopolymers due to limitation of petroleum resources and environmental concerns. Nano-fillers were used to reduce some drawbacks of biopolymers as packaging materials. Nanocomposite films composed of 5 % (wt% dry base) whey protein concentrate (WPC), 30 % glycerol, (1 %, 3 %, and 5 %) nano-SiO2(NS). The films were prepared by solution casting method. Tensile strength of WPC/NS nanocomposites increased around 50 % compared to WPC by increasing NS content up to 3 %. While elongation at break (EB) decreased around 20 % compared to WPC, simultaneously. But at high NS content (5 %), EB decreased to 17.93 %. Sensibility of WPC/NS nanocomposites film to water and water vapor permeability was decreased with increasing NS content up to 3 %. NS content was an effective factor on the color properties of the films. SEM micrographs revealed uniform distribution of NS into polymer matrix at low NS content. Consequently, crystallinity and thermal properties of the film were improved by adding NS content as compared to WPC film. It seems NS can improve some drawbacks of WPC such as mechanical weakness, hydrophilic properties as a packaging material and allowing the development of biodegradable bionanocomposite.
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