Examples Using Raman Fibre Optics

Raman fibre optics has been used to study the emulsion homopolymerisations of styrene and n-butyl acrylate (35). An IR spectroscopic technique for the examination of radical copolymerisations of acryl and vinyl monomers was developed. A comparative study of the copolymerisation of model monomer pairs was made using monofunctional and polyfunctional compounds. The data established the role of structural-physical transformations, involved in the formation of crosslinked polymers, on the copolymerisation kinetics and on the nonuniformity of distribution of crosslinks in the copolymers formed (151). Raman fibre optics of polymerisation of acrylic terpolymers was also used to monitor as well as an on-line measurement of morphology/composition (66). The high temperature (330 °C) cure reaction of 4-phenoxy-4 -phenyl-ethynylbenzophenone was monitored using a modulated fibre optic FT-Raman spectrometer (80). 

The time-dependent evolution of the polymerisation and copolymerisation reactions of styrene/unsaturated polyester resin was characterised using optical levitation with Raman spectroscopy (135). The n-butyllithium-initiated anionic polymerisation of styrene in ethylbenzene was measured using Raman spectroscopy (214). 

Raman experiments were performed on cationic photopolymerisations of a divinyl ether initiated with a diaryliodonium salt of hexafluoroantimonate photosensitised by anthracene. Isothermal Raman experiments were performed for a series of reaction temperatures and were used to determine the overall activation energy of the polymerisation reaction (240). 

A Raman spectrophotometer was used to measure in situ the polymerisation rate of acrylamide photoinitiated by hydrogen chromate anion in aqueous solution upon irradiation by laser beam (ionised argon) 

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In situ measurements in industry must be extrapolated to on-plant monitoring. The feasibility of using fibre optic coupling between the Raman experiment and the FT interferometer has been demonstrated. For on-line use special designed probes can withstand up to 300°C and 15,000 psi. Because Raman light can remotely be focused, it is even possible to measure in a non-invasive mode (for example through a specified reactor window). A portable process Raman analyser enables both in-line and at-line measurements. 

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