Is polyurethane sealant better than silicone?

22 / 11 / 2021

Is polyurethane sealant better than silicone?
With the accelerated upgrading of the construction industry, prefabricated buildings have shown a rapid development trend in recent years. As the first line of defense for external wall panel joint waterproofing, the performance of prefabricated building sealants is directly related to the waterproof effect of the project and it has attracted more and more attention.

There are many types of construction sealants on the market, according to the different basic polymers, they can be roughly divided into: silicone sealant (SR), polyurethane sealant (PU), and silane-modified polyether rubber (MS polyurethane sealers).
Here is another article about MS sealant, you can browse it How much do you know about the properties of MS sealant?

Today we are talking about silicone sealant VS PU sealant. 


What is polyurethane sealant?

Polyurethane sealant (Pu sealant) is mainly composed of polyurethane rubber and polyurethane prepolymer.
Polyurethane sealants are generally divided into two basic types, one-component and two-component
One-component Pu sealer is moisture curing type, the one-component Pu sealer is convenient for construction, but curing is slower.
Two-component Pu sealant is reaction curing type.; the two-component Pu sealant has the characteristics of fast curing and good performance, but it needs to be formulated during use, and the process is more complicated.

 

Advantage of Pu sealant

  1. Excellent Abrasion resistance
  2. High stability, wide adjustable range of performance
  3. Good adhesion, good strength, and tear resistance
  4. Good elasticity, excellent recovery, suitable for dynamic joints
  5. Strong anti-aging properties, service life up to 15 ~20 years
  6. Excellent oil resistance
  7. Resistance to biological aging;
  8. Polyurethane sealant price is moderate
  9. Cold resistance, good flexibility under low temperature conditions, Pu sealant will not freeze and crack in a cold environment
  10. Paintable
  11. Wide bonding range


Disadvantage of Pu sealant

 
1. Poor weather resistance (compared with silicone sealant) Polyurethane caulk is not heat resistant and cannot be kept in a high temperature environment for a long time, if urethane caulk is exposed to ultraviolet rays for a long time, it will accelerate the aging of the polyurethane sealant even cracks, bubbles and other conditions occurrence
2. When using polyurethane sealant in some occasions, primer is required and cannot be applied directly.
3. Polyurethane sealant is also relatively poor in water resistance, especially alkali resistance. If it is in an alkaline water environment, it will greatly affect the use effect.
4. Bubbles may appear that caused cracks in the adhesive layer during the curing process

Antas 293 Modified Polyurethane Sealant is neutral curing polyurethane sealant. It is safe and environment friendly with good weatherproofing ability. It shows good adhesion to concrete, aluminum, glass, and stone materials.

 

What is silicone sealant?

Silicone sealant (SR) is based on polydimethoxysiloxane as the main raw material, it is formed by curing elastic silicone rubber at room temperature
Silicone sealant can be divided into by its purposes: weathering sealant, structural adhesive, ordinary silicone sealant (MS sealant), special sealant (firestop sealant) , hole filling sealant (PU foam).
We have written an article about Structural sealant vs weather sealant

 

Advantage of silicone sealant

  1. Strong adhesion and high tensile strength
  2. Weather resistance, vibration resistance, moisture resistance, UV resistance and adaptability to large changes in cold and heat
  3. Broad applicability
  4. It can realize the bonding between most building materials
  5. Anti-aging
  6. No bubbles during cure

Disadvantage of silicone sealant

  1. Unpaintable
  2. Price is relatively high


What is the difference between polyurethane adhesive and silicone sealant in application?

 
Type Adhesive Elasticity Weather resistance Paintable Main Usages
SR Good Good Excellent Poor Bonding and sealing for windows, doors PVC and curtain wall
PU Good Good General Good Bonding and sealing for concrete and metal

Pu sealant:
  1. The connection of prefabricated concrete and other building materials and the filling and sealing of construction joints.
  2. The sealing and caulking between the wooden frames of doors and windows and the concrete of the walls
  3. The adhesive caulking of lightweight structures (such as curtain walls) on buildings
  4. Waterproof caulking of facilities like balconies, swimming pools, and bathrooms
  5. Sealing of air-conditioning and other system connections
  6. Sealing of heat-insulating double-glazing and heat-insulating window frames, etc.
  7. Sealing of automobile windows, bonding of auto parts, etc.
The main use of polyurethane sealant is in civil engineering and transportation, so it has some famous names: polyurethane joint sealant, pu exterior sealer, polyurethane concrete sealer, polyurethane adhesive, polyurethane caulk for windows, polyurethane caulk for concrete, exterior polyurethane caulk, polyurethane adhesive sealant etc.

Silicone sealant:
Silicone sealant contains both organic groups and inorganic Si-O structurehas which makes it has the stable chemical properties of both inorganic and organic materials, especially in the performance of excellent UV resistance, heat resistance and aging resistance. Silicone sealant has good compatibility with silicone structural sealant, and is widely used in weather-resistant sealing of building curtain walls.
With the rapid development of the building curtain wall industry, the special sealant for large plate glass and the special sealant for point curtain wall have also come to the fore.


Every adhesive is not flawless and has small drawbacks. For example, the puncture resistance of silicone sealant is not particularly good, and the price is relatively expensive.
The curing speed of polyurethane sealant is a bit slow, and the aging resistance is not very good.
The advantages and disadvantages of pu adhesive and silicone sealant are different, and the apply environment is different.

In the purchase process, not only the advantages of the sealant, but also the disadvantages must be considered. Integrate the advantages and disadvantages together, and see how cost-effective is and in which place it can be used. If you only consider the advantages and ignore the disadvantages, you may encounter trouble in use. Be prepared to avoid difficult problems.