Platinum Metals Review - Volume 41, Issue 2, 1997

Hydrosilylation is a reaction widely used in the silicones industry for the preparation of monomers, containing silicon-carbon bonds, and for crosslinking polymers, and results in a variety of products. Hydrosilylation reactions are catalysed by highly active platinum catalysts, such as the silicone-soluble Karstedt’s catalyst, which is prepared by the reaction of chloroplatinic acid, H2PtCl6, with vinyl-silicon containing compounds, such as divinyltetramethyl-disiloxane, M^vi M^vi – Inhibitors are widely used during hydrosilylation reactions to prevent premature crosslinking of polymers at ambient temperature, but permit rapid platinum-mediated crosslinking reactions at higher temperatures. Platinum colloids are formed at the end of the reaction and were identified by analysis. This paper discusses the mechanism of the hydrosilylation reaction, catalyst formation, characterisation, the effects of inhibitors and the range and complexity of the end products.

A new type of platinum:platinum-rhodium thermocouple wire which incorporates traces of yttrium in the platinum limb has been developed and tested in some typical working environments. This thermocouple possesses good thermal stability and mechanical strength at high temperatures, and a long service life, compared with conventional platinum:platinum-rhodium thermocouples. The thermocouple meets the output requirements of the Type S standard for thermocouples — those made of Pt:Pt-10%Rh — whose manufacturing tolerances are prescribed by the International Electrotechnical Commission (I.E.C.)(l). The life of thermocouples made from this wire is increased by around 1.5 to 2 times and they display a greater resistance to contamination.