Crystalline Emulsion polymerisation

Process monitoring using Raman spectroscopy (mainly in its NIR Fourier transform variant) is proposed for QA/QC purposes, on-line polymer analysis, in situ cure kinetics, emulsion polymerisation, non-invasive analysis of physical parameters (in situ crystallinity determination, etc.) and reactor compositions, real-time measurements, molecular interactions, and components in aqueous solutions. 

The monomer, 2-chlorobuta-1,3-diene, better known as chloroprene, is polymerised by free-radical emulsion methods to give a polymer which is predominantly (-85%) fr<2 s-l, 4-polychloroprene but which also contains about 10% cii-1,4- 1.5%, 1,2- and 1% of 3,4-structures (Figure 11.17). The commercial polymers have a Tg of about -A3°C and a of about 45°C so that at usual ambient temperatures the rubber exhibits a measure of crystallinity. 

With the exception of a few organic polymers, silica gel represents the basic material used to pack HPLC columns. The silica gel used for chromatography is quite different from crystalline silica (Si02), which is used for its preparation. It is prepared under conditions of controlled hydrolysis by polymerisation of tetraethoxysilane in the form of an emulsion giving rise to microspheres of uniform diameter in the order of 2 to 5 pm (Fig. 3.7). A sol-gel is formed in the process and these very small particles must grow in a regular manner in order to obtain the diameter of a few micrometres. The material has to be free of metallic ions. The silica gel particles obtained must be of uniform diameter to avoid the presence of preferential pathways in the packed bed in the column. 

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