How to Choose two component silicone sealant?

For over 40 years, silicone sealants have been used extensively in the construction market for applications requiring enhanced durability and strength compared to its predecessors, the organic-based sealants such as polyurethanes and polysulfides.

But not all silicone sealants are the same, so understanding their chemistries and basic cure characteristics is critical to selecting the right product for your next construction project.

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Silicone Chemistry

The silicone sealant’s unique polymer structure allows them to withstand movement, high temperatures and ultraviolent light (UV) exposure, making them an ideal solution for outdoor applications, such as curtainwalls, window perimeters and even highways.

Silicone sealants are defined by their cure mechanism, divided into acid and neutral cure categories.

• The acid cure (acetoxy) silicone sealants were the first to be used in the industry, and cure by contact with moisture vapor in the air, releasing acetic acid. This acidic vapor byproduct is corrosive and can cause compatibility issues with concrete and items in the glazing pocket. It can soften other sealants, etch glass and cause a chemical fog on the interior of insulated glass units. Due to this limitation, the construction industry is moving away from acid cure silicones and opening the market to neutral cure silicones.
• Neutral cure silicone categories typically include basic, alcohol and oxime cure mechanisms. While these silicones do produce a condensation byproduct, it is not as corrosive as the acid cure formulations. The industry prioritizes neutral cure silicones for exterior applications because of their ability to effectively bond with a variety of substrates.
  
  

One-Part and Two-Part Silicones

Silicones can also be broken down into one- and two-part categories, which have their own cure processes to take into consideration.

• One-part silicone sealants are used most often on the job site, as they cure by contact with moisture in the air. This process begins at the exposed surface first, then through the interior of the sealant bead until the cure is complete. This process can take up to 2-3 weeks depending on sealant depth, temperature and humidity.
• Two-part silicone sealants are utilized for in-plant applications, when speed is essential. After the two components are mixed, often through a large pump, the sealant cures uniformly throughout the entire bead, which takes only a matter of days.

You may find yourself with any of these silicone sealant types, depending on your application. But select the wrong one, and there could be serious compatibility issues, costing you significant time and money.

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If you are planning to use a sealant in your next project, you need to make sure you pick the best one for the job.

What Is a Joint Sealant?

A joint is where two different materials meet. A joint sealant is a substance used to seal or close the gap between these two materials. Its purpose is to prevent fluids, air, and other substances from getting through the gap while also allowing for limited movement. Joint sealants have several applications, including commonly in construction and building design.  

Choosing the Right Joint Sealant

Because a joint is a vulnerable part of a structure, the sealant for the joint needs to be the right product for the job or the consequences could be serious. With so many options, it can be hard to know here to start, but our guide to picking the correct joint sealant can help you make the right choice for your needs.  

Step 1: Consider the Requirements of the Job

There are so many different types of joint sealants with differentapplications. Before you start thinking about whichjoint sealer to use, you first want to have a clear understanding of what you need from your sealant. When choosing a joint sealant, it is important to consider the following: 

1. What type of substrates will be used?
2. Will the sealant be used on the interior or the exterior?
3. Will the joint be subject to any movement or vibration? If so, how much?
4. Does the sealant need to have any special resistances for the environment such as temperature extremes, moisture, UV light, or chemicals?
5. Will you be able to apply it quickly or will you need a longer open time?
6. Are you attempting to bond any difficult materials?
7. Will you need to paint over the sealant?

Only after you have answered these questions can you start to get a better picture of which joint sealant you need.  

Step 2: Review the Types of Sealants to Narrow Your Choices

After you have all the details on the requirements of the job, the next step to choosing the right product is to determine the joint sealant material that will work best. There are several different typesof sealants available with different properties and pros and cons.  

1. Latex– Latex sealants are water-based sealants that are inexpensive and easy to apply. They are easy to paint over, especially with latex paints. Latex joint sealants are a good choice for interiorjobs, but their uses are limited.

2. Acrylic– Acrylic sealants are solvent-based sealants. They are good for submerged joints, have reasonable UV resistance, and are easy to paint. A con of acrylic joint sealants is that they are not suitable for a lot ofmovement,so they tend not to do well on exterior projects.

3. Butyls– Butyl adhesives are synthetic rubber materials that have excellent adhesion with the majority of substrates, but they are not suitable joint glue for a lot of movement. They work well for interior projects but are hard to paint and should be kept away from any source of UV light. See this butyl sealant for acoustical and vapor barriers as an example.

3. Polysulfides– Considered high-performance sealants, polysulfide joint sealants are often used for industrial applications for interior and exterior purposes. They are especially favored in situations where chemical resistance is required orthe joint is submerged. If your joint is going to be experiencing cyclic motions, then it would be best to avoid polysulfide sealants.

5. Silicones– Silicone sealants are highly versatile and can be used in a wide range of applications including for both interior and exterior projects. Becausethey are particularly durable and remain flexible over time, they are an excellent choice for sealed joints that are likely to undergolarge amounts of motion. They also have a high UV resistance. The downside to silicone sealants is that they are unsuitable for submerged applications and are also not paintable. They are poor choices for brickwork but otherwise bond well with most other materials.

5. Polyurethanes (PU)– PU sealantsare the most versatile. The only applications they are unsuitable for are those involving glass. They are resistant to wear, paintable, and perform well on joints that have high levels of movement. The cons of polyurethane sealants are that they can be difficult to apply, and not surprisingly, they are the most expensive joint sealant.

Step 3: Think About Your Budget

Once you have narrowed down your joint sealant glue selection to one or two materials, the next step is to think about your budget. While an inexpensive joint sealant may be enticing, it may not hold up as well and could fail over time if it is the wrong product for the job. On the other hand, the most expensive choice may not be feasible with your budget.  

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Once you have taken into account these different considerations, you should be much closer to finding the right joint sealant for your needs.  

Case Study

Let’s try an example. You need a stainless-steel pipe thread sealant for a joint that will be inside a pneumatic drill. 

Step 1:Consider the requirements of the job.

You conclude that the sealant needs to work in exterior settings and be resistant to UV.It will be subject to large amounts of movement.The seal must also be durable and flexible.

Step 2: Review the types of sealants.

From the requirements, it seems clear you will need a high-performingthread sealant.Because of the heavy movement, your choices are limited to either silicone or PU sealant. 

Step 3: Think about your budget.  

PU sealants tend to be more expensive, and you just don’t think you have the budget for it. You decide to go for a silicone option that is marketed as being especially resistant to vibration.  

Let Us Help You Choose the Right Joint Sealant

If you have gone through these steps to pick a joint sealant but are still unsure of what to choose, that is okay. We want to help. Our customer service representatives are sealant experts who are happy to guide you to the right sealant solution for your job and budget. Give us a call at (855) 437- or fill out acontact form today.

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