Stability enhancement of shellac by formation of composite film: Effect of gelatin and plasticizers

The objective of the present study was to reduce the polymerization of shellac by the formation of composite films with gelatin. The 6% w/w of composite film based on shellac and gelatin was prepared by the incorporation of different concentrations of gelatin and was prepared by film casting method. The stability of the composite films was then studied at 40 °C, 75% RH for 180 days in a stability chamber and the physicochemical properties were investigated. The results demonstrated that the higher concentrations of gelatin (30%, 40% and 50%) contributed to slight change in the acid value and the percentage of insoluble solids upon 180 days of storage. These results were due to the protection at the active sites of the shellac, carboxyl and hydroxyl groups, by the electrostatic interaction between the negative charge of shellac and the positive charge of gelatin, resulting in the stabilized shellac. However, the mechanical properties could not withstand the storage time; further investigation was required to improve the stability in terms of mechanical properties of the composite film by the addition of a plasticizer. Two types of plasticizers were used: polyethylene glycol (PEG) and diethyl phthalate (DEP) represented hydrophilic and hydrophobic plasticizers at the concentrations of 5% and 10%, respectively. The addition of both types and concentrations of plasticizers could improve the poor mechanical properties and brittleness of the composite film for a longer storage time. However, only PEG 400 at 5% and 10% w/w acted as a good plasticizer capable of improving the stability of the composite film under the longer periods of storage. Therefore, the attempt to improve the stability in terms of polymerization and mechanical properties of shellac by the formation of the composite film and the addition of the plasticizer could be achieved. The result could be used to develop a new material for the various applications of edible films for coating in food and pharmaceutical industries.     

iso-Octane partial oxidation over Ni-Sn/Ce0.75Zr0.25O2 catalysts

In this study, Ni/Ce_0.75Zr_0.25O₂ catalyst was doped with different amounts of Sn by co-impregnation method. The catalysts were characterized by BET, H₂ chemisorption, XRD, TPR, TEM, XPS and tested for iso-octane partial oxidation (iC8POX) to H₂ in the temperature range of 400–800 °C at atmospheric pressure. The results showed that most of Sn species were present on the surface of Ni particles and did not modify the reducibility of the support. Addition of a small amount of Sn (<0.5 wt.%) lowered the catalytic activity for iso-octane partial oxidation by less than 5% while the extent of carbon deposition was decreased by more than 50%. However, Sn loadings higher than 1 wt.% caused a massive drop in catalytic activity. This indicates that as long as the Ni surface is only partially covered with Sn species, the active sites for the partial oxidation of iso-octane remain intact, while the surface site ensembles required for carbon formation are blocked.     

An approach for the enhancement of the mechanical properties and film coating efficiency of shellac by the formation of composite films based on shellac and gelatin

The purpose of this study was to enhance the mechanical properties and film coating efficiency of shellac by the formation of composite films with different concentrations of gelatin. The composite films were prepared by the casting method and their mechanical and physicochemical properties were investigated. The results demonstrated that the puncture strength and percentage elongation of the composite film increased from 3.61 to 15.58 MPa and from 3.80% to 32.47% as the gelatin concentration increased to 50% w/w, respectively, indicating the enhancement of the strength and flexibility of the shellac film. The efficiency of the composite film over two model substrates, i.e., hydrophilic and hydrophobic substrates, respectively, was also studied. The work of adhesion and spreading coefficient of the composite film increased from 66.42 to 83.53 mN/m and from −8.14 to −3.07 mN/m for the hydrophilic substrate, indicating the improvement of the coating efficiency whereas the hydrophobic substrate showed the opposite trend with the increase in gelatin concentration. Therefore, the formation of the composite film not only improved the mechanical properties of shellac but also enhanced the efficiency of film coating by the modification of different concentrations of hydrocolloid polymer to suit with the type of coating substrate. Hence the knowledge of composite film could make beneficial contributions to the various applications in film coating for the food and pharmaceutical industries.