Volatile By-Products of Silicone Curing
Formaldehyde Notice
In compliance with legislative requirements of 29 CFR 1910.1048 the statement must be made that Methylpolysiloxanes (silicone-methyl groups) can generate Formaldehyde when exposed to 300°F in the presence of air. This warning effects products which have the potential to expose workers to formaldehyde above .75 ppm for an 8 hour weighted average. There is no concern if silicone is not used above 300°F or in an oxygen rich environment.
This product contains methylpolysiloxanes which have the potential to form formaldehyde at 300°F in the presence of air. Formaldehyde is a potential cancer hazard and is a skin and respiratory sensitizer. Vapors irritate eyes, nose and throat.
Methods of monitoring formaldehyde exist in the form of Passive Dosemeters, Detector Tubes, etc. It is considered the user’s responsibility to specifically determine the actual level in their process and take the appropriate steps to safeguard employees.
Vulcanization
The vulcanization reaction of silicone polymer and peroxide curative results in the evolution of small amounts of volatile gaseous by-products. Proper ventilation is important to minimize employee contact with the gasses. Awareness of their presence can prevent subsequent adhesion problems of bonded assemblies.
Initial cure
- Moisture is liberated – less than 2%.
- Depending on the type of catalyst used, Dichlorobenzene and/or Dichlorobenzoic Acid may be released by decomposition of the catalyst – usually less than 20 ppm.
- Low molecular weight cyclic siloxane polymers are formed, typically Octamethylcyclotetrasiloxane and Hexamethylcylotresiloxane – usually less than 10 ppm.
Oven post cure
- Residual moisture is vaporized.
- The small residual amounts of Dichlorobenzene and Dichlorobenzoic Acid are vaporized.
- The low molecular weight cyclic siloxane polymers are volatilized and become silicon dioxide.
