Determination of Dihydroxybenzenes in Plastic Food Packaging Materials and in Food Simulating Liquids Using Capillary Electrophoresis

A capillary electrophoresis method has been developed to determine 1,2-dihydroxybenzene and 1,3-dihydroxybenzene in the food simulants distilled water, 3% acetic acid, 15% ethanol, and olive oil. Both substances, used as monomers and additives to make food packaging plastics, could be analyzed within 15 min. The 1,4-dihydroxybenzene isomer was unretained and eluted with the electroosmotic flow, and so the CE method can give only a semi-quantitative estimate of this isomer if it is present as a migrant. The analytical recovery for the 1,2- and 1,3-isomers from spiked simulants was good at 87% to 98% except for 1,2-dihydroxybenzene which could only be recovered to the extent of 58% from olive oil. Calibration graphs were linear and the limit of detection for each substance was 0.6 mg/kg, which is well below migration limits for these substances. It is concluded that CE offers a rapid and reliable analysis for the control of migration from plastics intended for food contact which employ 1,2-dihydroxybenzene or 1,3-dihydroxybenzene during manufacture, and offers a screening method for 1,4-dihydroxybenzene migration.     

Study on pyrolysis behavior and kinetics of waste plastics with spent FCC catalyst

Pyrolysis is the most promising method for treating plastic waste since it can convert waste plastics into high value-added products, which have significant application potential. In this study, kinetic and thermodynamic analyses of spent fluid catalytic cracking (FCC) catalysts were performed for testing their applicability in catalytic cracking of mixed plastics. Thermogravimetric analysis data were obtained at different heating rates under an inert atmosphere, and the synergistic effect between the mixed plastics and activation energy reduction before and after pretreatment of the spent FCC catalysts was discussed. Through a variety of model-free methods (Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Starink, and Kissinger methods), it is proved that the spent FCC catalyst facilitates the reduction in activation energy required for the pyrolysis of plastics, which is reduced by approximately 13% from 278 to 242 kJ/mol. The catalytic performance of spent FCC catalyst was improved after pretreatment, while its activation energy decreased by approximately 21% from 278 to 220 kJ/mol. The Friedman-Reich-Levi method was used to fit the curve, and the number of mechanism functions in plastic pyrolysis was determined according to the slope of the fitting curve. The C-R method was used in combination with the Malek method to determine the optimal mechanism function. Moreover, kinetic parameters of the spent FCC catalyst for catalytic cracking of plastics were obtained via kinetic studies on the pyrolysis of mixed plastics, which provided theoretical guidance for industrialization of plastic pyrolysis.     

Impact of microcellular plastics on industrial practice and academic research

Microcellular plastics (MCP) refer to any plastic with tiny bubbles of less than about 50 microns. It is made by subjecting polymers with a large amount of dissolved gas to a thermodynamic instability so as to nucleate a large number of cells instantaneously. MCP has been extruded and injection molded to make various industrial products. The fundamental theory for design of MCP and the processing methods are reviewed. It also discusses the design of equipment, including the die or mold, for MCP processing. The performance of MCP and the advantages of using MCP are presented. Some of industrial applications are also highlighted.     

聚氨酯泡沫塑料吸附-电感耦合等离子体质谱(ICP-MS)法测定地球化学样品中的痕量金

探讨了聚氨酯泡沫塑料的预处理、样品浓度、水洗条件、基体元素对金吸附率的影响等因素。结果表明,用泡沫塑料吸附含金量为5 ng~500μg的溶液,吸附率均在90%以上。影响聚氨酯泡沫塑料吸附率的重要条件是振荡前要用水充分浸透,水洗基体元素,矿渣宜在酸性环境下进行。铁、钛等离子可以提高吸附率,钠、钙、锌、矿渣等影响不显著,铝离子有微弱的抑制作用。ICP-MS的灵敏度与介质的雾化率有一定的相关性,应当使用硫脲介质的工作溶液作工作曲线,内标元素可用103Rh或185Re,但是对于高含量W样品,只能使用103Rh作内标。用金矿石国家标准物质做精密度与准确度验证,测定值与标准值无显著差异,相对标准偏差(RSD)均小于10%,精密度能满足地球化学样品中痕量金的分析要求。