Ahmed M. Youssef

Polymer Nanocomposites as a New Trend for Packaging Applications

Polymer nanocomposites markedly improved packaging properties due to their nanometer size dispersion. These enhancements include increased modulus and strength, decreased gas permeability, and increased water resistance. Additionally, biologically active ingredients can be added to impart the desired functional properties to the resulting packaging materials. Accordingly, polymer-based nanocomposites packaging materials with bio-functional properties have a huge potential for application in the active food packaging industry. In this review, recent advances in the preparation and characterization of polymer nanocomposites, and their potential use in packaging applications are addressed.

Preparation of Polystyrene Nanocomposites Based on Silver Nanoparticles Using Marine Bacterium for Packaging

Silver nanoparticles (Ag-NPs) were synthesized using marine bacterial isolate (MER1) culture filtrate and considered as eco-friendly nanofactories that meet many biotechnological applications. Ag-NPs were characterized by UV spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM) and impregnated into polystyrene (PS) matrix. The morphology of the prepared PS/Ag-NPs nanocomposites was characterized using SEM and TEM. Furthermore, the mechanical properties were evaluated. The prepared PS/Ag nanocomposites exhibited antimicrobial effect against gram-positive, gram-negative (G+ve, G−ve), yeast and fungal test microbe. These nanocomposites films can be used as food packaging materials.

Exfoliation of Kaolinite Nanolayers in Poly(methylmethacrylate) Using Redox Initiator System Involving Intercalating Component

Urea was intercalated into kaolinite (K) and the resulting modified clay (K-U) was characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and fourier transform infrared (FTIR). The K-U was added to promote the formation of Poly(methylmethacrylate)/kaolinite nanocomposites via in-situ intercalative emulsion polymerization of methylmethacrylate (MMA) in the temperature range 50–70°C using a redox initiation system based on urea as intercalatable component while potassium persulphate (PPS) was dissolved in the aqueous medium. Additionally, potassium persulphate/sodium bisulfite (PPS/SBS) as a powerful redox initiation system was employed in absence of any kaolinite form for comparison. The polymerization rate was found to increases slowly with the temperature but still lower if compared to the polymerization in absence of kaolinite, whereas the activation energy (Ea) decreased from 15.6 to 9.55 × 10 4 J/mol. On replacing the K with K-U, the rate of polymerization was faintly increased with the reaction temperature, also Ea was markedly influenced and reduced by factor of approximately 5 if a comparison was set relative to the polymerization in absence of kaolinite which highlights the role of urea as an effective intercalant that can constitute a redox initiation system in combination with PPS. The produced nanocomposites were of the exfoliated type as confirmed by XDR and Transmission electron microscope (TEM). In most cases, the nanocomposites exhibited improved thermal stability as compared with the pure PMMA at the temperature range 250–550°C, while the onset of degradation was not influenced as revealed by TGA. The DSC thermograms of PMMA/K-U nanocomposites did not show any transition and no clear T g was observed which contradicts with the pure PMMA which showed a small endothermic peak at 100°C related to the glass transition temperature, which implies the restricted molecular motion of PMMA chains in case of strong interaction forces between the dispersed silicate layers and the surrounding polymer phase where exfoliation exists.

Preparation and Utilization of Polystyrene Nanocomposites Based on TiO2Nanowires

Successful preparation of titanium dioxide nanowires (TiO2-NWs), by a hydrothermal method, then embraced in polystyrene (PS) to form nanocomposites using emulsion polymerization of styrene monomer in presence of different ratios of TiO2 nanowires. The morphology and crystalline structure of the prepared TiO2 were proved by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The thermal stability of the nanocomposites, measured by thermogravimetric analysis (TGA), was found to be upgraded especially at higher loading %s of the nanowires irrespective to pure polystyrene. Furthermore, polystyrene nanocomposites (modified with 4%, 8% and 12% of TiO2 nanowires) were used to remove organochlorine pesticide (OCPs) residues from contaminated water. GLC results showed that the pristine TiO2 nanowires has a poor affinity for removing OCPs residues (from 8.82 to 70%), whereas polystyrene/TiO2-NWs nanocomposites are powerful material for removing OCPs residues (61.76 to 98.64%) due to changing of TiO2 nanowires surfaces from completely hydrophilic to hydrophobic structure as proven by contact angle results. These nanocomposites materials can be used for packaging application and the mainly application of these materials in a water filter, which may be a promising and economically feasible technology for wastewater purification.

Catalytic Effect of Various Kaolinite Forms on the Emulsion Polymerization of Vinylacetate Using Acetone Sodium Bisulfite as Initiator

Kaolinite was intercalated with N-methylformamide (NMF) and dimethylsulphoxide (DMSO), separately. The intercalation of these species expanded the basal space of kaolinite from 0.72 to 1.08 and 1.13 nm, respectively as shown by the X-ray diffraction (XRD). Emulsion polymerization of vinylacetate (VAc) was carried out at different temperatures (60–80°C) using acetone sodium bisulfite as initiator in the absence and presence of untreated as well as the modified forrms of kaolinite (K-NMF, K-DMSO). The results revealed that the presence of kaolinite decreased the rate of polymerization (Rp) by factor of 4 at 60 and 70°C and 7 at 80°C and also the activation energy of polymerization (E a ) was decreased from 43.35 × 104 to 10.32 × 104 J mole−1 if compared with the polymerization of VAc in absence of kaolinite. Using the modified forms of kaolinite (K-NMF, K-DMSO) enhanced the Rp and reduced effectively the E a to − 27.92 and − 55.78, respectively. Conversely to untreated kaolinite, the Rp was declining with increasing the temperature in these cases. In all cases, Rp was the highest in the absence of any kaolinite form but in the same time the E a was also the highest. These results were discussed and explained on the basis of the catalytic activity of the different forms, radical scavenging nature of the kaolinite, and chain transfer.

Morphological, electrical & antibacterial properties of trilayered Cs/PAA/PPy bionanocomposites hydrogel based on Fe 3 O 4 -NPs

Bionanocomposites hydrogel based on conducting polymers were successfully fabricated from chitosan/polyacrylic acid/polypyrrole (CS/PAA/PPy) as well as the magnetite nanoparticle (Fe3O4-NPs) was prepared via co-precipitation method. In addition, different ratios of Fe3O4-NPs were added to the prepared bionanocomposites to enhance the antimicrobial and the electrical conductivity of the prepared conductive hydrogel. Furthermore, the morphology, the swelling percent, antimicrobial activity and the dielectric properties of the prepared conducting bionanocomposites hydrogel were investigated. The antibacterial activities of the experienced microbes were improved with the increasing the loading of Fe3O4-NPs in conducting Bio-nanocomposites hydrogel. Moreover, the DC-conductivity was examined and our resulted indicated that the DC-conductivity was enhanced by increasing the loadings of Fe3O4-NPs compared to that of the pure CS/PAA as well as CS/PAA/PPy.

A Novel Approach to Prepare Poly(Vinyl Acetate)/Ag Nanocomposite for Effective Antimicrobial Coating Applications

Polyvinyl acetate nanocomposites were successfully prepared based on silver nanoparticles. First, silver nanoparticles were directly prepared during the in situ emulsion polymerization of vinyl acetate monomer using AgNO3 as a source of Ag+ ions and poly(vinyl alcohol) was used for dual functions as emulsifier for emulsion polymerization and as a stabilizing agent, trisodium citrate (C6H5O7Na3) was used as reducing agent for Ag+ ions during the polymerization process. The prepared polyvinyl acetate/Ag nanocomposites were assessed using X-ray diffraction, scanning electron microscopy, Fourier transform infrared, transmission electron microscopy, and ultraviolet spectra. The antibacterial properties of the prepared polyvinyl acetate/Ag nanocomposites were investigated as antimicrobial activity against pathogenic bacteria, i.e., Staphylococcus aureus (G+ve bacteria) and Escherichia coli (G−ve bacteria). These polyvinyl acetate nanocomposites could be used as a promising material for enhanced and continuous antibacterial applications as coating and packaging materials. GRAPHICAL ABSTRACT