Microwave heating plastics

Applications The broad industrial analytical applicability of microwave heating was mentioned before (see Section 3.4.4.2). The chemical industry requires extractions of additives (antioxidants, colorants, and slip agents) from plastic resins or vulcanised products. So far there have been relatively few publications on microwave-assisted solvent extraction from polymers (Table 3.5). As may be seen from Tables 3.27 and 3.28, most MAE work has concerned polyolefins. 

Freitag and John [96] studied rapid separation of stabilisers from plastics. Fairly quantitative extraction (>90% of the expected content) of stabilisers from a powdered polymer was achieved by MAE within 3 to 6 min, as compared to 16 h of Soxhlet extraction for the same recovery. MAE and Soxhlet extraction have also been compared in the analysis of cyclic trimer in PET [113]. On the other hand, Ganzler et al. [128] compared the extraction yields for various types of compounds from nonpolymeric matrices for microwave irradiation with those obtained by the traditional Soxhlet or shake-flask extraction methods. Microwave extraction was more effective than the conventional methods, in particular in the case of polar compounds. As expected, the efficiency of the former is high especially when the extraction solvents contain water. With the high dipole moment of water, microwave heating is more... 

Bishop CS, Dye A. 1982. Microwave heating enhances the migration of plasticizers out of plastics. J Environ Health 44 231-235. 

Badeka, A.B. and Kontominas, M.G. (1996). Effect of microwave heating on the migration of dioctyladipate and acetyltributylcitrate plasticizers from food grade PVC and PVDC/PVC films into olive oil and water, Z. Lebensm. Unters. Forsch., 202, 4, 313-317. 

Badeka and Kontominas (1996) reported the efifect of microwave heating on the migration of di(2-ethylhexyl) adipate from food-grade PVC into olive oil and water. Migration was dependent on heating time, microwave power setting, the nature of the food simulant and the initial concentration of the plasticizer in the film. 

McCluggage, W. G., Roddy, S., Whiteside, C., Burton, J., McBride, H., Maxwell, P., and Bharucha, H. 1995. Immunohistochemical staining of plastic embedded bone marrow trephine biopsy specimens after microwave heating. J. Clin. Pathol. 48 840-844. 

The chapter begins by introducing the concepts behind microwave heating and the properties that make plastics transparent to this kind of radiation. This is followed by a definition of microwave pyrolysis of plastics and the ways that microwave transparency of plastics can be overcome in order to use this microwave energy as a source of heat for pyrolysis. A number of microwave pyrolytic processes for materials other than plastics are also introduced. 

Mixing carbon with microwave-transparent materials, particularly plastics, and subjecting the mix to microwave radiation, is a very efficient way to heat up such materials, increasing their bulk temperature to a point where pyrolysis occurs. In this chapter the main characteristics of a number of microwave pyrolysis processes, for plastics and other materials, have been introduced, showing that these processes combine the advantages of microwave heating with the commercial and environmental opportunities intrinsic to the pyrolysis of wastes. 

Nowadays, many advanced techniques are available in the ceramic industry to coat a solid layer onto a solid surface or to make ceramic materials with special properties [99-1 IS], such as spin-coating [99], chemical vapor deposition [100-106], and chemical vapor infiltration [106-109], thermal spray [110-112], plastic spray [113], and spray-coating [114]. The deposition can be caused by conventional heating, by laser beam, or by microwave heating. 

The following points are relevant to the operation of a microwave oven. Plastics and Pyrex glasswares do not contain polar molecules and are therefore not affected by microwave radiation. (Styrofoam and certain plastics cannot be used in microwaves because they melt from the heat of the food.) Metals, however, reflect microwaves, thereby shielding the food and possibly returning enough energy to the microwave emitter to overload it. Because microwaves can induce... 

Galotto MJ, Guarda A. Suitability of alternative fatty food simulants to study the effect of thermal and microwave heating on overall migration of plastic packaging. Packag Technol Sci 2004 17 219-223. 

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