The difference between potting silicone condensation type and addition molding

Condensed type
The condensation type silica gel is cured by absorbing moisture from the atmosphere during the curing process, and cannot be accelerated by heating (it is disadvantageous to add too much heat during curing). Usually a small amount of by-products are produced during the curing process. These two factors indicate that condensation-type curing can only be carried out when the compound is opened in the atmosphere. Sealing into the enclosed space before the curing is completed can have an adverse effect. This chemical is commonly used in one-component sealants, coated adhesives and single/two-component potting compounds.
One-component condensed silica gel (RTV) is not suitable for applications where the thickness exceeds 10 mm because it cures to form a waterproof membrane and prevents the silicone at the bottom of the shell from solidifying.
One-component RTV silica gels are cured into elastomers using a variety of crosslinkers that produce by-products, some of which can be hazardous to sensitive electronic components. Therefore, we recommend the use of a dealcoholic and ketonic one-component RTV silica as the encapsulating material.
Recovery: Condensation-type cured silica gel using an organotin curing agent can be chemically decomposed to a liquid form under specific circumstances. The recovery process begins when the silica gel is placed in a completely sealed container for a prolonged period of high temperature heating (eg, 6 months at 60 ° C or 6 months at 90 ° C). If the compound is exposed to the atmosphere due to certain routes, recovery will not occur, but high temperature resistance (up to 300 ° C) is possible.

Addition molding
The addition-cured silica gel is cured using a platinum curing agent and does not produce any by-products during the curing process. Once the curing agent is added, they will cure themselves, even in a closed container, without opening to the atmosphere. The two-component addition molding gel can be cured at room temperature, and if necessary, it can be heated to accelerate the curing speed without any adverse effect on the cured colloid. Single component addition molding silica usually requires heat curing.
Platinum curing agents are susceptible to infection when attacked by specific chemicals, inhibiting curing and resulting in incomplete curing. The uncured rubber should avoid contact with the following chemicals during the mixing process or during the production process: nitrogen, sulfur, phosphorus, arsenic, organotin curing agent, PVC stabilizer, epoxy resin curing agent, vulcanized rubber and condensation type silica gel (note The dealcoholized RTV silica gel does not cause uncured).
Addition molding silica also requires good chemical balance to achieve the proper physical properties of the cured colloid. Therefore, before weighing out, the two components of A&B should be thoroughly stirred. At the same time, the correct mixing ratio is also very important. Since A&B is usually produced in a co-production, it is not recommended to mix two different batches of compound.