Spiros Tzavalas

Infrared Spectroscopy as a Tool to Monitor Radiation Curing

Photoinitiated polymerization of multifunctional monomers and oligomers is one of the most efficient methods to produce quasi-instantly highly cross-linked polymer networks. It has found a large number of commercial applications, mainly in the coating and printing industry. Among the advantages of this technology the high cure speed, the reduced energy consumption, and the absence of VOC emissions are the most remarkable. It is well known that the UV curing can be performed either by a radical or a cationic mechanism. The cationic photoinduced process presents some advantages compared to the radical one; in particular lack of inhibition by oxygen, lower shrinkage, good mechanical properties of the UV cured materials, and good adhesion properties to various substrates [Fouassier & Rabek, 1993]. The properties of a UV-cured material depend not only on the photocurable composition but also on its photopolymerization kinetics, it is very important to have access to an analytical technique that will facilitate this purpose.

Semiconductive polymeric coatings for outdoor polymeric insulation

In the following paper the development of a semiconductive coating for medium voltage outdoor insulator is presented. The coating based on silicon rubber and semiconductive fibers shows resistivity in range of 10 MΩ/□ which allowed for increasing of the insulator temperature 8 °C above the ambient after energizing with 12 kV. Outdoor testing was performed at Koeberg Insulation Pollution Test Station. The developed coating presented superior performance compared to a standard outdoor epoxy insulator. Moreover in contrary to traditionally made ceramic glazes the semiconductive coating shows positive thermal coefficient of resistance (PTCR) eliminating the risk of thermal runway.