PU Silicone: Understand Everything About These Sealants!

What is the difference between PU and silicone?

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There are many differences between PU and silicone, although they are very versatile materials, each of them has its respective advantages and disadvantages, which will determine the most suitable application for each one.

Starting with the silicone sealant, the benefits are excellent resistance to weather conditions, especially UV, resistance to oxidation, no yellowing over time, has excellent properties in terms of electricity and fire, in addition to having a high movement capacity.

Silicone sealant also has some limitations, such as, it is not paintable, it has marked odors depending on the type of cure, it accumulates a lot of dirt on its surface and has a low resistance to tearing.

Pu sealants are widely used in civil construction, but this type of sealant also has its limitations and benefits, as does silicone sealant.

The benefits are high resistance to puncture, tear and abrasion, paintable, low odor during curing, and high movement capacity.

As for the limitations, it has a low permeability to gases, which delays its curing somewhat, compared to silicone sealant, does not have good properties at low temperatures, can yellow over time, has limitations in high temperature applications, and does not have as good UV resistance as silicone sealant.

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What does silicone pu mean?

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As I explained to you, silicone doesn't mean much when it comes to the definition of a product and its chemical basis. Silicone PU ends up being a common construction term that can be dangerous when specifying the correct sealant or adhesive for a specific stage of the work.

When we talk about silicone or PU, it is necessary to understand each of them a little more thoroughly. Here I will explain a little more about the types of PU and silicone that exist and also how the types of curing influence the final quality of the application.

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What are the types of PU?

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PU sealant can have a wide variety of applications, depending on the formulation adopted by the manufacturer. In addition to the final application, the shape of the pus cure may also vary.

The pu sealant can have its bicomponent composition, cured through isocyanate, or it can also be monocomponent, known in the construction market for hybrid sealants or hybrid polyurethane sealant.

Within the construction market, these are the two most commonly found and used types, from sealing expansion joints on facades and floors, to gluing glass to facades, known as glazing.

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What are the types of silicone?

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Unlike PU, silicone does not vary as widely as the formulations for application in sealants and adhesives. Basically, what defines the application of silicone sealant are its types of curing.

The types of silicone sealant curing will influence the substrates where it will have greater adhesion and also compatibility between different materials in a system where sealing is necessary.

In the Brazilian market, we can easily find three types of silicone sealants, namely:

• Acetic Silicone Sealant: silicone sealant that will release acetic acid during its curing process
• Neutral Silicone Sealant: The most common neutral silicone sealant in Brazil is the oxymic-curing one, which releases oxime. This is a compound that ends up having a pH around 7, that is, neutral.
• Alcoholic Silicone Sealant: it also has a neutral cure, as well as the oxymic one, but it releases methanol during its curing process.

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What is silicone pu used for?

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Silicone and PU, in construction, can have different applications, but each one will have technical advantages over the other depending on the location applied.

We can divide their use into two groups, to simplify the choice of the chemical base, the first being resistance to weathering. If the sealant is directly exposed to weather conditions, especially to the Sun, the product that will best resist is the silicone sealant, but be careful, it is important to choose the right type of cure for the application.

The second point, also one of those that weigh the most on the choice decision, is whether the sealant can be painted. Theoretically, this type of limitation should not interfere with the choice of sealant, since it is purely aesthetic. But if it is essential, the polyurethane sealant is the one that must be chosen.

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What is the drying time of PU silicone?

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The drying time of silicone and pu is different, both because the chemical bases are different and the type of formulation adopted.

If both products are monocomponent, which cure in contact with atmospheric air humidity, the silicone sealant tends to cure faster than the pu sealant.

This is due to the fact that silicone sealant is more permeable to gases than pu sealant, making the curing process faster under the same temperature condition.

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Summarizing all the information about silicone pu

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PU silicone is a name popularly adopted by the construction market, which does not reflect the correct name of the material, nor does it reflect the correct technical specification of the products.

Silicone ends up being confused with sealant, while silicone is a chemical base just like pu. In this case, there may initially be only two alternatives, silicone sealant or pu (polyurethane) sealant.

By understanding this basic information about the definition of the class of the material, adhesive or sealant, and of the chemical base, silicone or pu, it is possible to start specifying the correct material for your work in the correct way and reduce the chances of choosing the wrong material.

If you want to know more about sealants, I recommend reading our Complete Guide to Sealants and if you have any questions, contact our support team and remember, Blok it's here, for any challenge.