Liquid Silicone Rubber Types: One-Part, Two-Part, Condensation and Addition Cure
Liquid silicone rubber needs no complicated mixing or molding equipment. At room temperature or with mild heat, it cures into an elastomer either by picking up moisture from the air or by being mixed with a crosslinker. Two classification schemes are in common use: by packaging, and by cure chemistry.
By packaging: one-part and two-part
A one-part product contains everything in a single package and is applied as supplied. A two-part product comes as parts A and B that are mixed in the specified ratio before use.
By cure chemistry: condensation and addition
Condensation-cure systems crosslink through a condensation reaction that releases small by-product molecules, and the subtypes are named after those by-products. Addition-cure systems crosslink by addition and release no small molecules.
RTV and LTV
- RTV (room-temperature vulcanizing): condensation-cure systems and a few addition-cure systems cure into an elastomer at room temperature.
- LTV (low-temperature vulcanizing): most addition-cure products need gentle heating to cure quickly.
Overview
| Packaging | Cure chemistry | Subtypes |
|---|---|---|
| One-part | Condensation (RTV) | Acetoxy, alkoxy (alcohol), oxime, amide, amine, acetone |
| One-part | Addition (LTV) | - |
| Two-part | Condensation (RTV) | Alkoxy (alcohol), dehydrogenation, amine |
| Two-part | Addition (RTV, LTV) | - |
When choosing a system, start from the site conditions: whether heating is possible, how much working time is needed, and whether by-products are a concern. Then narrow the choice using the table above.