A Flash Point Behavior of Dimethyl Silicone Liquids

In order to understand why dimethyl silicone liquid of 50 centistokes, whose flash point is more than 300°C, undergoes ignition, the volatile products evolved during heating at 300°C in a controlled atmosphere were identified by GC-MS analysis. It was determined that a cyclic oligomer, D3 was dominant of the oligomers identified. The boiling point and flash point behavior of D3, D4, etc. were measured. From these results, it is suggested that D3 plays a decisive role in the igniting process. On the grounds that the decrease in evolution of volatile products would result in some improvement in the flash point behavior, a chelate compound of cerium was added to inhibit the decomposition of the silicone liquid. It was concluded that the flash point behavior can be improved somewhat by the addition of this compound, suggesting that the chain rearrangement reaction could be inhibited to evolve less of the cyclic oligomer, D3.