(42b) Evaluation of Filler Containing Si-H (Silicon hydride) Formulations for H2 off-Gassing Risks during Production and Packaging

Silicon compounds containing silicon-hydrogen bonds including chlorosilanes, Si-H silicone fluids and Si-H emulsions play a key role in a wide range of applications from aerospace to textiles. Numerous types of fillers are added into the Si-H containing products to gain added functionality. When fillers are added into the Si-H containing formulation, it can cause Si-H compounds to liberate H₂ due to basicity of the filler. H₂ liberation could present a major risk from drum bulging to explosion or fire. Understanding how to evaluate filler Si-H interaction and paying detailed attention to equipment design, operating procedures, storage and shipping conditions are critical to mitigate the H₂ off-gassing associated risks.

In this study, commonly used fillers were evaluated in Si-H containing formulations using thermal screening unit (TSU) and gas chromatography (GC). The filler pH level was measured as received and compared with the manufacturer technical data sheet. The study investigated various scenarios including temperature ramp up during shipping, temperature increase during production and packaging. The results showed that 1 kg of finished Si-H containing product could liberate up to ~0.02 mole of H₂ during the first 10 hours after filler is added into the Si-H system. H₂ off-gassing could also cause thicker products to swell by as much as 30% of its original volume which could potentially cause production or packaging vessel overflow.

The key finding is that fillers with alkaline impurities could trigger unintended H₂ evolution from the Si-H containing compounds. Controls such as passivating production vessels, installing pressure relief valve device on the packaging line, using vented packaging containers and leaving sufficient headspace in the packaging containers could be used to mitigate the risks.