Spectra techniques

Turbidity spectra and size exclusion chromatography (SEC) are two techniques which could be used for the on- and off-line monitoring of polymer particle size during the polymerization. An experimental evaluation of the two techniques is reported herein and it is shown that they satisfactorily follow the change of the particle size during the reaction. Information from SEC analysis is exploited to experimentally evaluate the turbidity spectra technique and investigate its potential to be used as an on-line measurement of particle size for latex reactor control. 

Fig. 17. Diagrams a-c illustrate different experimental methods for measuring the dichroism needed to calculate the orientation function - see text for discussion of (a) two spectra technique, (b) differential technique and (c) waveplate technique...

At your instructor s option, obtain an infrared spectrum using salt plates (Technique 25, Section 25.2). Compare the spectrum with the one reproduced in Experiment 13. The spectrum of your esfer should have similar features to the one shown. Interpret the spectrum and include it in your report to the instructor. You may also be required to determine and interpret the proton and carbon-13 NMR spectra (Technique 26, Sections 26.1 and Technique 27, Section 27.1). Submit your sample in a properly labeled vial with your report. 

ABSTRACT. The use of mass spectrometry to collect data on the decomposition chemistry of nitramine compounds and the relevance of the data to the processes occurring in these materials when they are used in actu propellant and explosive applications is discussed. The simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and time-of-flight (TOF) velocity-spectra techniques and then-application to the study of energetic materials are discussed. The means by which these techniques enhance the amount of information obtained from more conventional mass spectrometric experiments is illustrated with studies on the evaluation of the use of appearance energy measurements to study the thermal decomposition of HMX and on the identiHcation of the HMX pyrolysis products and the determination of their gas formation rates. 

Figure 6. Illustration of the TOF velocity-spectra technique used to determine the molecular weights of the pyrolysis products contributing to the ion signals at m/z=46 from a hypothetical decomposition of HMX.

The STMBMS and TOF velocity spectra techniques enhance the use of mass spectrometry in the study of the decomposition of energetic materials. The careful control of the reaction environment in these experiments allows the identification of the pyrolysis products and accurate measurement of their gas formation rates to be made. Correlation between the observed products and the macroscopic and microscopic processes occurring within the reaction cell will allow qualitative models to be created that may explain the processes leading to the formation of the various products. Hopefully, these results may be correlated with the more limited results gathered from experiments conducted under more severe conditions (i.e. shock initiated reactions or quenched combustion experiments) to provide further insight into the mechanisms controlling the combustion of these materials under their operational conditions. 

Searle, N.D. Activation spectra techniques and applications to stabilization and stability testing of materials. In Ketola, W.D., Evans, J.D. (eds.) Durabihty 2000 Acceltaated and Outdoor Weathering Testing, p. 41. ASTM, West Conshohocken, PA (2000)... 

Gordy W and Cook RL (1984), Microwave Molecular Spectra Techniques of Chemistry Volume XVIII 3rd edn. New York Wiley Interscience. 

Software (CD) for processing multiple spectra techniques (NMR, MS, UV-Vis, IR, Raman, GC, HPLC)... 

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