COMMON SEALANT FAILURES AND BOSTIK’S SOLUTIONS

In the construction market, proper sealant installation is important to ensuring a safe and successful building project. However, although a product may be properly installed, it still can be subjected to influences that could make it not perform as desired. Let’s take a look at common causes for premature sealant failure and Bostik’s solutions:

1. Incorrect Sealant Selection

When choosing a sealant, some of the important items to consider are its long term adhesion ability to the desired substrate, what substrate it is and the sealant and substrate’s chemical compatibility.

A common premature sealant failure can occur when bonding to self-adhered flexible flashing. Initially, the adhesion may look acceptable. However, when exposed to the elements (high temperature in particular), a failure can occur to the interface of the flashing wrap if the wrong sealant is used.

Another failure can occur if an acetoxy or acid curing, silicone adhesive is installed on cementitious substrates or window perimeter joints for concrete or masonry surfaces. Furthermore, a polyurethane sealant should not be applied over existing silicone sealants.

While these sealants may appear to work at first, not considering these important items can result in damage to the structure.

The Bostik Solution

Bostik recommends getting a jobsite adhesion test done prior to choosing a sealant. This test provides:

• Comprehensive evaluation of the jobsite
• List of jobsite anomalies
• Illustration of possible installation deviations
• Possible eligibility for Bostik’s Gold Seal Warranty

Each of these items helps the contractor better understand the job and sealant product need prior to installation.

2. Sealant and Joint Movement Capabilities

Other items to consider are the sealant and joint’s movement capabilities over a wide range of temperatures. A sealant may initially appear to work for a joint application until the substrates are subjected to the elements. If the sealant applied doesn’t allow for the appropriate movement and has improper joint configuration, adhesive or cohesive failure may occur.

Determining movement can be especially difficult when two substrates are adjacent to each other in a particular joint detail. Common mistakes can include using a butyl sealant in dynamic, expansion joints in precast construction. Additionally, copper has different amounts of movement vs. concrete or glass during a temperature change.

The Bostik Solution

Bostik designs and manufactures products to comply with pre-determined movement capability. Engineers and architects are responsible for determining total joint movement. However, the key is to specify and use sealants that are within the movement needs of joints on a project. Bostik’s Pro MS 50 offers superior total joint movement capability of 100% (+/-50%).

3. Inadequate Sealant Temperature/UV Resistance for Needed Application

Prior to selecting a sealant, it’s important to understand the product specifications. A sealant may initially appear to work in median temperatures but fail to perform properly once temperatures drop or increase.

In cold temperatures, joints are at their widest, causing the sealant be in a tension mode (stretched). Conversely, in hot temperatures, joints are usually at their narrowest, since substrates have expended due to movement by thermal forces.

Additionally, a sealant that does not have UV resistance is likely to fail if exposed to the sun over time.

The Bostik Solution

Bostik manufactures a full range of high-performance sealants. Included in our product palette are one and two-component polyurethane and MS-based sealants such as Pro MS 50.

Pro MS 50 in particular is an innovative and high-performing sealant that can comepete in some of the silicone sealant application areas. For example, it has stay white color properties in the presence of UV light while having the inherent ability to be painted to meet aesthetic demands. and Pro MS 50 T exhibit great resistance to UV.

For more information on Bostik’s sealant products for the construction market call 800-7-BOSTIK.

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