Determination of antioxidants in polymeric materials.
A review of methods proposed for the analysis of antioxidants in polymeric materials, cast in the form of a step-by-step examination of the problems involved in any scheme of analysis, with a critical appraisal of the published procedures designed to overcome them.
Mass spectrometric analysis of additives in polymer extracts by desorption chemical ionization and collisional induced dissociation with B/E linked scanning
Abstract Desorption chemical ionization in combination with collisional induced dissociation and B/E linked scan proved to be a viable method for identifying additives in polyethylene extracts by mass spectrometry. In comparison with fast atom bombardment (FAB), much less fragmentation was observed with desorption chemical ionization (DCI) using ammonia as reagent gas. Furthermore, most likely due to the “matrix effect”, not all the additives in the extracts were detected by FAB. The softness and the lack of matrix effect make ammonia DCI a better ionization technique than FAB for the analysis of additives directly from the extracts. Most likely due to higher collision energy, product ion mass spectra acquired with a double focusing mass spectrometer provided more structural information than the spectra obtained with a triple quadrupole mass spectrometer. Besides contamination from the seals of the supercritical fluid extractor, high and low density polyethylenes extracted with supercritical carbon dioxide produced similar results as with toluene.
Numerical Simulation of Induction Heating Process of Continuous Casting Slab
Compared with traditional blazing furnace, the Continuous Casting-Direct Rolling is an advanced manufacturing steel technology, which can reduce energy waste, decrease pollution and enhance efficiency. The characteristics of steels during induction heating are complex, the change of material properties with temperature makes exact analysis methods very difficult to implement. Therefore, a powerful computer aided numerical tool (i.e., finite difference analysis) is selected to numerically model the induction heating process in this paper. The mathematic model coupling with electromagnetic field and thermal field was established, and it was solved by finite difference method (FDM), thus the slab temperature distribution and its variation with time were obtained, and the characteristics in whole induction heating process were studied. To validate the program feasible, the results were evaluated and compared with experiment results, which showed that the simulation results are reliable and effective. The skin effect in heating process from the two results was studied and demonstrated, the temperature change caused by different parameters such as the induced power intensity and the corner radian were also presented, which indicate that the slab temperature can be heated uniformly through adjusting these parameters, thus the continuous casting slab can meet the rolling requirement.