Silicone potting adhesives are divided into one-component and two-component potting adhesives according to the main materials and additives, and can be divided into condensation-type and addition-type potting adhesives according to the curing reaction. So today let’s talk about what are condensation and addition silicone potting compounds? What is the difference between the two?
Under normal circumstances, the potting compounds for waterproofing are condensed, and the addition-type potting compounds are generally used for thermally conductive potting. Condensation type potting glue shrinks greatly, at the same time will release a certain amount of alcohol, and the curing time is also very long, so the addition type is more environmentally friendly, the addition type potting glue can be food-grade, and can be cured at room temperature cured.
What is a silicone condensation potting compound?
Silicone condensation type potting compound is a kind of silicone rubber that is cured by moisture in the air and mixed catalyst. The curing time mainly depends on the amount of catalyst. The more the amount of catalyst, the faster the curing speed. However, shrinkage and by-products are released during curing.
Compared with the traditional condensation-type potting silicone rubber, the addition type silicone potting compound has no small molecular by-products in the vulcanization process, the cross-linking structure is easy to control, the shrinkage rate of the vulcanized product is small, and the product process performance is superior. It can be vulcanized at room temperature, and it can be vulcanized under heating conditions, and it can be quickly vulcanized in deep layers. The product has good processing performance, low viscosity, good fluidity, can be poured, can be pumped and statically mixed, and has the advantages of simplified process, fast, high efficiency and energy saving The advantages. Therefore, it has developed rapidly since its emergence, and there is a trend to replace condensed silicone potting materials.
What is a silicone addition type potting compound?
Addition type potting compounds are cured with a curing agent, and no by-products are produced during the curing process. Once the curing agent is added, they will cure on their own, even in an airtight container, and do not require exposure to the atmosphere to do so. The silicone two-component addition type potting compound can be cured at room temperature. If necessary, the curing speed can be accelerated by heating, and will not have any adverse effect on the cured colloid. One-part addition silicones usually require heat to cure.
It is also important to note that uncured compounds should avoid contact with the following chemicals during mixing or production: nitrogen, sulfur, phosphorus, arsenic, organotin curing agents, stabilizers, epoxy curing agents, vulcanized rubber and condensed silicone , otherwise it will inhibit curing and lead to incomplete curing.
Silicone addition potting compounds also require a good chemical balance to achieve the proper physical properties of the cured colloid. Therefore, both components should be thoroughly mixed before weighing out. At the same time, the correct mixing ratio is also very important. Mixing of two different batches of compounds is not recommended as they are usually produced in sets.
The Difference Between Condensation and Addition Silicone Potting Compounds
Firstly. Curing depth
After the two components of the addition type potting glue are mixed evenly, the glue is poured, and the curing process is consistent as a whole, that is to say, the thicker the glue is, the thicker the overall curing is. Moisture participates in the reaction, curing is carried out from the surface to the interior, and the curing depth is related to moisture and time, so in application, it is generally not suitable for condensation-type potting compounds to fill or encapsulate products with deep or thick thickness.
Secondly. heating application
Increasing the curing speed of the silicone potting compound can improve the production efficiency, so many users increase the baking process, which greatly speeds up the time of the next process, but this process is only suitable for the use of the addition type silicone potting compound, and the condensation type The curing of the encapsulant requires two key conditions, namely moisture and catalyst, which have no obvious relationship with temperature.
Thirdly. the adhesive properties
When the silicone potting compound needs to have certain adhesive properties during the application process, the condensed silicone potting compound is preferred, which has good bonding properties with most materials and will not have edge debonding. Phenomenon, the addition type of silicone is slightly worse.
In addition to the above differences, for example, condensed silicone encapsulant is stronger than addition type in terms of anti-toxicity; for food-related applications, addition type is selected, and there is no molecular volatilization. If you need to further explain the application selection and application problems between the two in detail, please leave a message to Nuofeng NFION, and we will definitely answer it for you.