PU (Polyurethane) Sealant: Learn Everything About It!
Have you heard about PU sealants or polyurethane sealant? If you work in the construction business, this issue is certainly part of your daily life!
But do you really understand how this product works and all its features?
Before anything else, we know that information is never too much and that is what makes the difference to achieve your goals and guarantee excellent results!
So, thinking about it, we thought it would be very useful to prepare this article to exhaust this subject and provide more knowledge so that you can obtain better results. Are you ready? So let's go!
What is Sealant?
To begin with, we need to clarify what sealant is, since we are going to discuss one type of them, which is PU sealant.
In general, the sealant consists of a material that has the function of sealing joints and openings between substrates, preventing water, air or other substances from entering or leaving the structure, accompanying the natural movement of the substrates.
The ability of sealants to move along with the substrate, where it was applied, is the great difference between sealants and adhesives!
Do you want to understand more about sealants? Access our other article, by clicking here.
What is PU Sealant?
Now, you're ready for us to get into the main topic of this article! Let's understand about PU sealant?
Polyurethane sealants, popularly known as PU sealants, have been able to enter the market slowly, since the 1960s.
However, the 80s were marked by the great increase in polyurethane sealants and, today, they are the most used types of sealants in Brazilian civil construction.
This is due to the very versatility of urethane, which allows the formulation of a wide range of products.
Therefore, PU sealant can be defined as a type of sealant, with urethane in its formulation, giving its particular and specific characteristics of this material.
What is PU Sealant for?
The popularity of PU sealant in construction is no wonder, its performance characteristics greatly favor application at various stages of the works.
The pu sealant has a high resistance to wear and abrasion. For this reason, polyurethane sealants are used to seal horizontal joints on surfaces with traffic.
A very common example is the application of sealing expansion joints on floors, sidewalks, squares, malls, patios, and floors of concrete in factories, buildings, or any other area subject to light vehicle traffic.
It is also possible to have polyurethane sealants with formulations adapted to withstand heavy traffic, such as expansion joints on highways and airports.
Another great advantage of most pu sealants is that they are paintable immediately after curing. Allowing to apply this type of sealant to surfaces where it will be necessary to repaint the substrate frequently.
Benefits x Limitations
Not every material or product is perfect, is it? Therefore, I will list the main advantages and disadvantages of pu sealant, in an easy way, so that you can read and make the right decisions in your work.
Benefits of PU Sealant:
- High moving capacity and high elastic recovery
- High puncture resistance, high tear resistance and high abrasion resistance;
- Low cost;
- Low gas permeability, if you want to form a barrier against gases, this is the best option;
- Excellent resistance to microbiological attack;
- Low odor;
- Good adhesion to various substrates.
PU Sealant limitations:
- Low gas permeability, so this will bring a slower cure to the monocomponent sealant;
- Poor performance in low temperature applications;
- It should not be applied to damp or wet surfaces;
- Limited high temperature resistance;
- Wide range of formulation, can lead to the most diverse qualities of pu sealant.
What is PU glue used for?
The pu sealant is also known as pu glue, popularly.
Here it is worth remembering the difference between a sealant and a glue, regardless of the type of material used.
The PU sealant has the function of sealing the spacing between two surfaces, sealing them against water and gas infiltration, when necessary.
The pu sealant must also have another important characteristic that differentiates it from a pu glue, which is the ability to conform and adapt to surface movements.
Now, a pu glue, or a pu adhesive, has a different application, a pu glue or adhesive, has only the characteristic of joining two surfaces that have low movements.
Even so, a product that is both a pu sealant and a pu glue is possible. This category of products is known as structural sealants, used both for bonding surfaces and also for sealing between them. A very common example of this application is gluing windshields to car structures.
What is PU sealing?
As I said above, pu sealant is extremely versatile in terms of the applications in which it can be used.
Depending on the formulation developed, it can be used from expansion joints on highways and airports, to expansion joints on building facades or places with low traffic.
Apart from those applications that require a greater effort, the pu sealant can also be used in applications where there is a low movement of the structures and, consequently, a lower requirement for the sealant.
These applications are considered sealing applications only, so the use of a sealant or sealing is highly recommended. This type of sealant does not have to have a high moving capacity, since there will be very little.
In this case, a very important characteristic is to assess whether the chosen sealant will adhere to both surfaces. If it doesn't, the sealing role of the structure becomes flawed.
What is PU 40 for?
PU 40, PU 30, PU 35, PU 55, these are nomenclatures that you may have already seen. Am I right?
Well, sealants are classified according to some physico-chemical characteristics, one of which is the chemical base, in this case the pu and the other is its hardness.
The hardness of sealants is measured by Shore hardness, and most of the sealants we use here in Brazil use the A scale, so in the product data sheets there are Shore A 40 hardness, Shore A 30 hardness, and so on.
I explained all of this to arrive at the next point. PU 40, is nothing more than the classification of the pu sealant, with a Shore A hardness of 40.
It is important to remember that hardness is directly related to the elastic modulus of the sealant. Don't you understand what this is and how it can affect the choice of the ideal sealant for your work? Then click on this link, which I explain in another article the importance of choosing the sealant in the correct way.
What is the difference between silicone and PU?
Here comes the great doubt of many people. What is the difference between silicone and PU? It seems to be very simple, but there are many people who still don't know the difference between them and what each one represents in isolation.
I say this because I constantly hear people who still ask for “silicone pu” or “silicone pu” and that's wrong.
The difference between silicone and PU is that they are chemical bases on which sealants can be formulated, for various applications. Just as there are sealants made from other bases, such as acrylic, used to manufacture acrylic sealants.
That said, there is the family of silicone sealants and that of polyurethane sealants or PU sealants, while PU silicone is wrong.
Summary of PU Sealant
In this article I compiled the main and most relevant information that I believe is important for you to be able to understand and apply in his works!
I explained from the basic definition of what a sealant and a PU sealant are. In addition, I have listed the main applications of the pu sealant.
I separated the benefits and limitations of PU sealant, this part of the article is very important for you to understand and never make mistakes in your works again!
PU glue and pu sealant are known to be the same material, but the definition of glue and its application is very different from that of a sealant. That's why I decided to explain this topic a little better and help you not buy the wrong product!
PU for sealing and PU 40, two very common names in construction sites, but most people don't know the differences and here I explained, so that there are no more doubts.
Silicone PU does not exist, and here I explained everything in detail, so that you can always choose the best product for its construction.
I prepared all this material to help you, a construction professional, who is always seeking more knowledge to evolve. Count on me and on Blok for any challenge you have in your works!
If you have any questions, leave them in the comments below and I will answer them.
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