Current approaches to waste polymer utilization and minimization: a review

The mass production of polymer products, in particular plastics, and their widespread use depending on the inherent advantages they have, make these materials ironically a threat to life on Earth. Polymer recycling is being considered as one of the most widely accepted remedies to the threat of growing amounts of plastic waste by both the public and scientists. In practice, recycling is associated with many difficulties, such as problems related to separation, sorting and cleaning operations, lack of fiscal subsidies, instability of selective garbage separation programs, high transport and electricity costs, etc. Still, a large section of society and the authorities agree on the necessity and importance of recycling to protect the environment, and natural habitats and resources for future generations in a balanced manner to conserve raw materials, and to reduce energy consumption, municipal solid waste production and greenhouse gas emission. The recycling effort is almost endless in itself and includes a variety of approaches such as refurbishing, mechanically reshaping, chemically treating, thermally utilizing, etc. Some novel approaches such as application in carbon capture or synthesis of carbon nanostructures from the plastic waste are among the new process technologies of recycling. From traditional and promising polymer waste utilization approaches, this review will highlight sustainable methods to reduce impacts of plastic waste on the environment. © 2018 Society of Chemical Industry     

Color stability of bulk‐fill composites immersed in different drinks

Bulk‐fill composites show structural differences compared to those of conventional resin composites. Their more reactive photoinitiators, monomer compositions, and increased filler content may result in higher color stability than for conventional ones. Therefore, this study aimed to assess the color stability of three different bulk‐fill composites and one conventional resin composite with a higher filler load after 1 week and 1 month of immersion in different drinks. The resin composite materials that were tested demonstrated significantly different color changes after immersion in the four solutions during both evaluation periods. Immersion in coffee and red wine showed noticeable staining of all the materials. The discoloration effect of staining solutions on the resin composites depends both on the material composition and on the pigment types found in the solutions.     

Application of gaseous ozone to control populations of Escherichia coli, Bacillus cereus and Bacillus cereus spores in dried figs

The effect of ozonation as a method to reduce Escherichia coli, Bacillus cereus and Bacillus cereus spores in dried figs was investigated. Dried figs were sprinkle inoculated with E. coli, B. cereus and B. cereus spores in sterile bags at a level of 10(7)microorganism g(-1), mixed and allowed to dry for 1h at 25 degrees C prior to ozonation. Inoculated samples were exposed to gaseous ozone in a chamber at 20 degrees C and 70% relative humidity. Ozone concentrations of 0.1, 0.5 and 1.0 ppm up to 360 min were used to inactivate E. coli and B. cereus while 1.0, 5.0, 7.0 and 9.0 ppm ozone concentrations for 360 min were used to treat B. cereus spores. E. coli and B. cereus counts were decreased by 3.5 log numbers at 1.0 ppm ozone concentration for 360 min ozone treatment. Up to 2 log reductions in the number of B. cereus spores were observed above 1.0 ppm ozone concentration at the end of 360 min of ozonation. No significant changes in color, pH and moisture content values of dried figs were observed after the ozonation treatments. No significant changes were found between sweetness, rancidity, flavor, appearance and overall palatability of ozonated and non-ozonated dried figs. Ozonation was found to be effective especially in reduction of vegetative cells in dried figs and a promising method for the decontamination of dried figs.     

Effect of gaseous ozone on microbial inactivation and sensory of flaked red peppers

Flaked red peppers inoculated with Escherichia coli , Bacillus cereus and B. cereus spores were exposed to gaseous ozone at 20 °C and 70% relative humidity (RH). Ozone concentrations of 0.1, 0.5 and 1.0 ppm up to 360 min were used to reduce E. coli and B. cereus, whereas 1.0, 5.0, 7.0 and 9.0 ppm ozone concentrations for 360 min were used to treat B. cereus spores. When flaked red peppers were treated with 1.0 ppm ozone concentration for 360 min, B. cereus and E. coli counts were decreased by 1.5 and 2.0 log numbers, respectively. Bacillus cereus spores were reduced by 1.5 log numbers at ozone concentrations of 7.0 ppm or above for 360 min. There were slight changes in flavour, appearance and overall palatability of flaked red peppers treated with ozone between 5.0 and 9.0 ppm. Ozone concentration (1.0 ppm) for 360 min can be used to decrease E. coli and B. cereus, whereas ozone concentrations ≥5.0 ppm can be used to reduce B. cereus spores.     

Graft copolymerization of methyl methacrylate upon gelatin initiated by benzoyl peroxide in aqueous medium

The graft copolymerization of methyl methacrylate upon gelatin was studied using benzoyl peroxide as an organic initiator in aqueous medium. The grafting reactions were carried out within the 65–90°C temperature range, and the effect of monomer and initiator concentrations on the graft yield were also investigated. The maximum graft yield was obtained at a benzoyl peroxide concentration of 0.20 × 10⁻² mol/L and the optimum temperature was 80°C. Thermogravimetric analysis showed that the thermal stability of gelatin increased as a result of grafting. Further, such changes in the properties of methyl methacrylate‐grafted gelatin as density, moisture regain, and water uptake were also determined. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1547–1556, 1999     

Improving low fat meatball characteristics by adding whey powder

In this study whey powder (WP) at levels of 0%, 2% and 4% was added to beef meatballs formulated with 5%, 10% and 20% fat levels. Raw and cooked meatballs were analyzed for protein, fat, moisture, ash and pH. Meatballs were evaluated for cooking characteristics, juiciness, colour parameters (L*,a*,b*) and sensory properties. Addition of WP did not affect fat and protein contents of meatballs. Addition of 2% or 4% WP significantly increased cooking yield regardless of the fat level. Both fat level and WP level significantly affected fat retention values of meatballs. Incorporating WP had no effect on meatball juiciness. Addition of WP increased fat and moisture retention of meatballs. Twenty percent fat resulted in higher L* and lower a* values. Adding WP resulted in higher L* values but WP had no effect on a* and b* values. WP had no detrimental effect on sensory properties.     

Conversion of CCl2F2 (CFC-12) in the presence and absence of H2 on sol–gel derived Pd/Al2O3 catalysts

Conversion of CCl₂F₂ in the presence (hydrogenolysis) and absence of hydrogen was investigated on Al₂O₃, AlF₃ and Pd/Al₂O₃ xerogel and aerogel catalysts. CCl₂F₂ was found to form CClF₃ and CCl₃F on Al₂O₃ and AlF₃ in the presence and absence of hydrogen as well as on the Pd/Al₂O₃ catalysts in the absence of hydrogen. Overall activity increased during the hydrogenolysis reactions at 230°C as a function of time which was paralleled by a significant increase in the yield of CClF₃ formed through a Cl/F-exchange reaction. X-ray diffraction patterns of the spent catalyst recovered after 3 h of hydrogenolysis confirmed the presence of Pd(C) (Pd–carbon solid solution) and AlF₃ phases on Pd/Al₂O₃ catalysts indicated that the carbon incorporation into the Pd lattice and the transformation of Al₂O₃ to AlF₃ starts at the initial stage of the reaction. It was concluded that AlF₃ is responsible for the Cl/F-exchange reactions. CH₄, a complete hydrogenation product, is formed during hydrogenolysis. Another route for its formation is the reaction between hydrogen in the gas phase and the interstitial carbon.