Why not use lightweight, inexpensive closed-cell backing?
This permanent compression set results after a single 3-hour cycle with the material compressed to 1-1/2" and heated to 150-deg.F (i.e. -25% of nominal size per movement claim at a very commonly experienced summer substrate temperature).
Benchmarks of Performance for High-Movement Acrylic-Impregnated, Precompressed, Foam Sealants When Considering Substitutions
EMSEAL's SEISMIC COLORSEAL has set the standard for high-movement (100% of nominal size) precompressed foam sealants. The product is unique in its proven performance capabilities.
Other than EMSEAL, there is only one US-based manufacturer of precompressed foam sealants. This other manufacturer while offering its own branded products also private-labels their isobutylene-and-wax-base saturated products to all (nine (9) at last count) other US-based expansion joint manufacturers who claim these products as their own.
This bulletin describes why the performance of EMSEAL's microsphere-modified, 100% acrylic impregnated precompressed foam sealant is different and unique. It also offers simple testing procedures that validate these claims and that reveal the shortcomings of both wax and asphalt-based technology predecessors.
The primary drivers of
the performance of SEISMIC COLORSEAL are:
EMSEAL's own asphalt-compound impregnations as well as the wax-saturations of other alternatives are not capable of the same performance.
Should you encounter products being offered with the same performance claims, we would encourage that these claims be tested and certified to the same performance conditions described in this bulletin.
We believe these conditions to accurately reflect those expected to be achievable in applications for which the material is being specified and installed. We are interested in ensuring that your design and performance expectations are met. Should you wish to comment on the basis of following testing or the assumptions made, we would very much appreciate your feedback at firstname.lastname@example.org.
The chemical emulsion fills (in the case of saturation) or coats (in the case of impregnation) the cells of the foam. The foam in turn provides the elastic memory that ensures an inherent active backpressure. The amount of emulsion put into the foam affects the degree to which the mechanical back-pressure of the foam is dampened or deliberately restrained.
Some dampening is essential to slow the expansion rate of the foam in order that the product can be practically installed into a pre-constructed joint opening. Too much dampening can negatively affect the product's ability to expand as the joint opens when temperature drops.
Impregnation vs. Saturation:
Saturation, by contrast, fills the foam cells completely and relies on less foam but a greater amount of chemical emulsion to achieve a seal. This approach has worked historically in some markets where climate and design practice limits the movement range to which the product will be subjected.
Hybrid Precompressed Sealants:
Asphalt, Wax, Acrylic--The Evolution:
Movement, Recovery, and Trade-Offs:
this reason EMSEAL has never claimed that the foam backing is performing a
waterproofing function in the 100% movement-capable SEISMIC COLORSEAL
product. Instead, the acrylic-impregnated foam provides:
Claims of 100% movement capability AND watertightness in the foam backing AS WELL AS high temperature stability in combination with compression should be treated skeptically.
Why Use Impregnated Open-Cell Foam Instead of Just Closed-Cell Foam? Impregnated, open-cell, foam is used as the backing because it features very low compression set. Compression set is the permanent loss of the ability to self-expand that results after a material is subject to normal compression cycles. Compression set is made worse by simultaneous exposure of a material to heat.
Closed-cell foams suffer on average 25% permanent compression set under movement and temperature cycles typical in construction applications.
Consequently, attempts by EMSEAL more than 25 years ago, as well as repeated more recent attempts using closed-cell foam backings show that this approach does not offer a viable comparable alternative to impregnated open-cell products.
Despite this loss of active backpressure to compression-set, closed cell backed materials are being offered as inexpensive alternatives to the impregnated, open-cell backed products. These products usually are offered with a more conservative 50% of nominal movement capability. They are by that limitation not comparable. Regardless, because the material is not supplied precompressed, and because compression-set further limits the recovery, closed-cell based hybrids should not be considered equals to impregnated foam sealants.
1. Movement Capability: 100% of nominal material size. More explicitly this 100% is comprised of -50% compression AND +50% extension from nominal size. This means, for example, that 2" nominal material has the capability to be compressed to 1-inch and extend to 3-inches during the thermal cycling of a substrate.
2. Application and Substrate Suitability: These materials are offered for use in applications involving porous substrates such as concrete, brick, stone, etc. and non-porous substrates such as the metals used in curtain walls and metal panels.
3. Active Backpressure: Precompressed sealants are claimed to actively recover as the result of the stored-strain energy of compression in the foam backing.
Typical descriptions include “back-pressure inherent in the elastic open-cell foam backing.”, and “works under its own constant internal pressure”.
Stability and Resistance to Bleeding: High temperature stability
of 185°F (85°C) is typical.
Given that if specified and installed into a condition that will utilize the full movement claim of the material, it is reasonable to expect that the products can be compressed down 50% from their nominal size and that this condition will occur during achievable high temperatures on a building.
Actual substrate temperatures on dark-colored substrates like bronze or black curtainwall mullions, on a Southerly exposure, during the peak mid-day hours, in summer, are regularly recorded at around 180o F (82o C). For purposes of this testing, 180o F (82o C), and 185o F (85oC) was used, as was a more widely experienced 150o F (65o C).
Given that these products claim the ability to follow joint opening movement through their inherent backpressure, and that if specified and installed into a condition that will utilize the full movement claim of the material, it is reasonable to expect the material to recover unassisted from the compressed state achieved at the claimed high temperature stability point to the maximum of its claimed movement range.
1) Six-inch long pieces of 2-inch (50mm) nominal material are removed from their shrink-wrap and hardboard packaging, and any mounting-adhesive release liners are removed.
2) The samples are installed between the faces of identical, aluminum, clamping jigs.
3) By tightening the bolts in the clamping jigs, the samples are compressed down to 1” (the -50% movement claim. This dimension would be achieved in actual applications during the heat of the summer as joints close due to the expansion of adjacent structural materials).
4) The samples are placed on a metal baking sheet, in a scientific oven, tilted at an angle of 30 degrees.
5) The samples are then baked at 150-deg.F for 3 hours. (This temperature chosen to simulate a south-facing, summer season, mid-day exposure on a dark-colored, metal substrate like a window mullion).
6) After 3 hours, the oven door is opened and the samples observed for signs of instability of the impregnation and/or any change in the material.
7) The samples are allowed to cool to room temperature.
8) The clamping jig bolts are loosened to allow the samples to recover. The recovery of the material over the next 24-hours and beyond is observed.
As the temperature slowly drops to room temperature the substrates are moved slowly apart. The acrylic-impregnated SEISMIC COLORSEAL begins immediately to self-expand and the silicone bellows achieves expansion to 3-inches (75mm) within 3 hours while the acrylic impregnated foam backing expands to beyond 3-inches (75mm).
While there remains a place in the market for low-movement, moderate-temperature applications for asphalt or wax-based products, many of today's construction environments and applications call for higher performance.
Consequently, should you be specifying an impregnated foam sealant product we suggest you require proof of movement capability and temperature stability in combination, and incorporate the following language in your specifications:
substitute candidates to be certified in writing to be free in composition
of any waxes or asphalts, wax compounds or asphalt compounds. All
substitute candidates shall be certified in writing to be:
Once again, your feedback as to the conditions of performance used to validate our claims, or challenges to facts presented are invited. Please send them to email@example.com. Thank you.
For complete guide specifications for EMSEAL products, please go the individual product pages at our Product and Application Index.
Last Modified: May 06, 2013