Process monitoring and quality assurance of polymeric materials by computerized pyrolysis mass spectrometry

The potentialities of computerized pyrolysis mass spectrometry (m.s.) are discussed for applications in process monitoring and quality assurance involving nonvolatile materials such as polymers. The traditional obstacles to more widespread acceptance of pyrolysis m.s. for industrial applications are reviewed in the light of recent developments which provide a major reduction in the cost, size and complexity of the equipment. Rapid advances in computerized data reduction, evaluation and interpretation methods for complex mass-spectral patterns are also transforming the classical “fingerprinting” concept of pyrolysis m.s. into a much more detailed compositional and structural characterization approach. These new developments are illustrated by means of several practial examples ranging from quality control of clinically important polyurethanes to monitoring of wood pulping processes and of growth phenomena in microbial cultures.     

Gasanalyse

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Synthesis of Manganese Oxide Microspheres by Ultrasonic Spray Pyrolysis and Their Application as Supercapacitors

Manganese oxide (MnO₂) microspheres are prepared using an ultrasonic spray pyrolysis (USP) process. A mixed solution of potassium permanganate and hydrochloric acid is nebulized into microsized droplets, which are then carried by air flow through a furnace tube. Each microdroplet serves as one microreactor and produces one microsphere. Upon heating, KMnO₄ is decomposed into MnO₂ microspheres; this synthetic process can easily be scaled up. Characterization of the MnO₂ microspheres by scanning electron microscopy, transmission electron microscopy, powder X‐ray diffraction, Raman spectroscopy, and X‐ray photoelectron spectra is described. Different morphologies of MnO₂ microspheres can be controlled by tuning the precursor concentrations (and ratios) and furnace temperatures. Microspheres synthesized at 150 °C give amorphous MnO₂ while synthesis at 500 °C yields crystalline α‐MnO₂. The electrochemical properties investigated by cyclic voltammetry give specific capacitance as high as 320 F g^?1, demonstrating promising properties as supercapacitors. In addition, these microspheres can be directly sprayed on conductive substrates, such as carbon fiber paper, and may have useful applications as a supercapacitor electrode coating. The supercapacitive properties of MnO₂ microspheres at higher charge and discharge rates can be improved by increasing the surface area coverage or coating them with a thin layer of conductive polymer.     

Impact of perforation impedance on the transmission loss of reactive and dissipative silencers

The effect of perforation impedance on the acoustic behavior of reactive and dissipative silencers is investigated using experimental and computational approaches. The boundary element method (BEM) is applied for the prediction of transmission loss of silencers with different perforation geometries. The variations are considered in the porosity (8.4 and 25.7%) and hole diameter (0.249 and 0.498 cm) of perforations for both reactive and dissipative silencers, as well as the fiber filling density (100 and 200 kg/m3) for the latter. The acoustic impedance for a number of perforations in contact with air alone and fibrous material has been incorporated into the predictions, which are then compared with the measured transmission loss using an impedance tube setup. The results demonstrate the significance of the accuracy of the perforation impedance in the predictions for both reactive and dissipative silencers.     

Synthesis of “capped porphyrins”

The synthesis of “capped porphyrins” ($\text{10}$), ($\text{18}$), and ($\text{28}$), and their (chloro)iron(III), iron(II), cobalt (II), and zinc(II) complexes is reported. These complexes serve as models for the active site of the oxygen binding haemoproteins. In addition to reversible binding of dioxygen by each of the iron (II) porphyrin complexes, the 1-methyl-imidazole-(“C₃-capped porphyrin”) iron (II) complex ($\text{23}$) reacts reversibly with carbon monoxide, in solution at 25°C.     

The complete closed coexistence curves for 2H,3H,6H,7H,8H-5,8-(Dimethylmethano)-5(R)-methylquinoxaline with water and with deuterium oxide

The complete closed solubility curves for 2H, 3H, 6H, 7H, 8H-5,8-(dimethylmethano)-5(R)-methylquinoxaline with water and with deuterium oxide have been determined. With water the lower critical solution temperature (LCST) was found to be 51.4°C and the critical solution temperature (CST) was found to be 215.0°C. With deuterium oxide the values were 40.4°C for the LSCT and 221.7°C for the CST. The deuterium oxide curve completely encompassed the water curve. Solution compositions at the critical temperatures were also determined.     

Veränderung des dielektrischen Relaxationsspektrums von Hochpolymeren mit der Verstreckung

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