Foam tapes are often gauged by a variety of physical properties; compression, compression set, density, and tensile strength. One of the important properties is temperature resistance. As foam tapes become more readily utilized throughout a large variety of industries, temperature performance becomes critical in deciding which tapes are best suited to which applications.
Engineering for Hot and Cold Applications
Though elevated temperature resistance is the most common attribute when testing foam tapes, foam tapes are also needed for cold temperature applications. Foam tapes can be used throughout cold temperature environments such as truck and trailer applications, refrigerated facilities, and construction.. These tapes must be able to be used in temperatures that may sometimes be lower than -20 degrees Fahrenheit. On the other end of the spectrum, tapes may need to be used in very high temperature environments, particularly for under the hood automotive and transportation applications. These foam products need to resist temperature cycling from cold to extremely hot and maintain their integrity and ability to seal. Some common temperature performance data for acrylic, polyurethane and polyolefin foams are listed in the table below.
Note: The temperature data is general and not specific to any one product.
Accommodating Expansion and Contraction
Foam tapes can experience both expansion and contraction as the temperature rises and falls. Not only must foam tape be rated for specific temperature extremes, it must also be tested for intense variations within those extremes. Some foam tapes are going to be held at a consistently high or consistently lower temperature. Others need to be able to resist cycling within a temperature spectrum. The best bonding tapes accommodate the expansion and contraction of the materials that they are bonding. This is a feature that makes foam bonding tapes superior to other methods of bonding, such as mechanical fasteners or other adhesives. In this situation, the foam tape operates as a buffer, distributing stress and offering additional flexibility.
Bonding, Sealing, and More
Foam tapes are designed to bond and seal in one easy application. (many foam tapes require some type of compression but not all). When you look at these properties in conjunction with temperature resistance, the number of applications can be astonishing.
Specialty tape products are often needed whenever temperature extremes are going to be present. Foam tapes are tested to varying temperature extremes, and different tapes may be necessary depending on the application’s needs. Tom Brown, Inc. has a wide variety of foam tape products, including Saint-Gobain, 3M, Foamseal, and Adhesives Research series.
Structural spacer tapes are used alongside one or two part structural silicone sealants to ensure that glass remains bonded to the metal framing system for the life of a building. The controlled density and thickness of a spacer tape provides a highly consistent gap or channel into which the silicone sealant is applied. A diagram of a typical application is shown below:
What might not be obvious is how the cell structure in the spacer tape enables the silicone sealant to cure.
How Structural Silicone Sealants Cure
One part silicone sealants are formulated with all the ingredients needed to reach a cured state (paste phase to rubber phase). The curing process is initiated by a reaction with moisture in the air. One part systems are low cost and easy to use and apply.
Two part sealants separate the reactive portion or catalyst from the base adhesive formula and then join them together via a mixing and pumping process. Two part systems lend themselves to higher volume, higher speed operations where quick handling and cure time are needed in an assembly operation.
Both one and two part sealants outgas and do generate small amounts of VOCs (volatile organic compounds); even the low VOC grades.
Spacer Tape Cell Structure and Sealant Curing
Closed cell foams consist of a series of unbroken chambers or cells which resemble small inflated balloons in a compact configuration. Closed cell foams are very strong durable materials but they don’t permit the passage of air or moisture through the foam matrix.
Open cell foams by contrast have cell walls that are broken with air filling the spaces in between. This series of “broken cells” create a pathway for the movement of air, moisture, and VOCs.
Examining the chart below tells the story of why cell structure is so critical.
High WVTR values like those seen above allow moisture to reach the one part system to facilitate curing and simultaneously provide a pathway for the escape of VOCs from the bond area.
Structural spacer tapes and silicone sealants are made to work hand in hand. Each truly enables the other and when done correctly, long lasting, reliable, structural silicone glazed facades will result. Want to know more about structural spacer tapes? Call Tom Brown, Inc. for samples or a quote.
Foam bonding tapes feature a variety of core materials and it can be a bit bewildering as to why.
The most common types of foam core chemistries are:
The foam core performs several vital functions within the bond area:
- It distributes loads over a large area enhancing energy absorption
- Improves stress relaxation
- Compensates for substrate mismatch and lack of planarity
- Enhances conformability
Each core chemistry offers a unique set of properties making it suitable for certain applications. The best way to visualize this is by observing the stress strain curves of each type:
(Photo Courtesy of Saint Gobain )
Advantages and Applications for Core Chemistries
(Photo Courtesy of Saint Gobain )
Want to learn more about how foam bonding tapes can provide multiple benefits over traditional mechanical fasteners and liquid adhesives? Contact Tom Brown, Inc. today.
The term “glazing tape” is frequently used throughout the residential and commercial window industry and it can mean very different types of products to different users.
If you’re in the curtain wall or window wall segment, the “glazing tape” you refer to would be a “structural glazing tape”. This type of tape uses a high strength, monolithic, foamed acrylic adhesive system that can bond an insulated glass unit into a metal framing system. The acrylic foam is very viscoelastic and gives high elongation properties allowing it to effectively handle the varying loads of wind and weather.
If you are a commercial glazier or fabricator making or installing storefronts, low rise office buildings, and schools, the “glazing tape” you refer to might also be called a “spacer tape” or “structural glazing spacer”. This tape relies upon a semi-rigid, open cell polyurethane foam core that allows air and moisture to reach the structural silicone sealant that is the primary system bonding the glass unit in place. The open cell structure allows the silicone to cure and reach maximum bond strength. This is an example where tape and sealant work hand in hand to deliver the best of both worlds.
If you’re a manufacturer of residential windows, the “glazing tape” you use will likely be made from a polyethylene (PE) or polyvinyl chloride (PVC) core that has been coated with an acrylic or rubber –based adhesive system. These are lower density materials that are easier to compress to form a seal for the window. They are more economical than the commercial type products and are well suited to the sizes and loads common to residential windows.
So as you can see, “glazing tape” is a rather broad term that covers many different yet high performing products. Want to learn more about all of these products from 3M, Saint Gobain, and Adhesives Research? Contact Tom Brown, Inc. for samples and to have your questions answered.