Precast Sealant Tapes and Joint Systems

Sealing Telecomm Shelters

Telecommunication shelters must be watertight. Liquid sealant (caulk), alone, is not protection against long-term water infiltration. Backing up the caulk with UST Impregnated Sealant tape will provide lasting protection. Not only do telecomm shelters house critical electronics, but telecomm shelters are usually located at the full mercy of the weather. Extremes in heat, cold, as well as pummeling from rain, snow, sleet and driving winds leave these critical structures totally exposed.

In the highly competitive market of telecomm shelter manufacturing, a watertight, maintenance-free sealing solution is an essential offering.

Product Description

UST is a preformed expanding foam tape sealant. It is made by impregnating a resilient, high-density, open-cell polyurethane foam with water-based, stabilized acrylics. It is supplied factory precompressed and packaged in reel form with self-adhesive backing for use in preformed joints subject to expansion and contraction movement, and also as gaskets in tightly squeezed, non-moving joints.

After removal of packaging, material begins gradual expansion–slowly in cold weather, faster in hot.

Sealing ability is a function of the characteristics of the open cell foam structure, the level of impregnation, and the degree of compression or density which can be varied to suit specific applications. For example, lower compression serves for dust, driving snow, etc., while progressively greater compression is required for vertical run-off water, etc.

UST is supplied precompressed to less than the nominal material size for easy insertion into a preformed joint of the same opening width.

Sealing between the foam and substrate is achieved through a combination of the pressure-sensitive adhesive impregnation and the back pressure of the expanding foam.

Why liquid sealants alone are not a watertight solution

While they provide aesthetic benefit, liquid sealants (caulk) lose effectiveness for many reasons:

poor initial adhesion to exposed aggregate
poor adhesion caused by dust and concrete particles
failure to create “hour-glass” required for proper liquid sealant performance
failure to tool sealant to promote proper adhesion
loss of key physical properties (UV resistance, modulus) over time and temperature.

Furthermore, structures sealed with liquid sealants must be recaulked as an ongoing maintenance commitment. This is difficult and extremely costly given the often remote location of these units.

For these reasons, providing a secondary seal of impregnated foam sealant will ensure that leaks do not occur even when the caulk fails.

Liquid sealants (caulking) are widely misused. They do not work to fill voids, cannot function if too much is used, and cost manufacturers a fortune in wasted material. UST does fill voids and can be used to control liquid sealant depth thereby eliminating waste and ensuring a geometry that will allow the liquid sealant to function.

Precast Sealant Tapes and Joint Systems

liquid sealant on exposed aggregate precast

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Liquid sealant relies on a very precise depth to width ratio to work. If out of spec it will fail at the bond line as seen above.

Choice of a low-cost sealant can lead to big-cost damage.

Unlike liquid sealants that squeeze out, EMSEAL precompressed sealants compress into themselves. On exposed aggregate precast faces, a sealant that conforms to the irregular substrate is essential.

Features

Will not dry out and become hard or brittle.
Durable, resilient, therefore suitable for moving joints.
Tolerant of joint face irregularities.
Ideal as a secondary seal to wet sealants (caulk).
Compatible with and adheres to most wet sealants.
Does not bleed.
Back pressure of foam maintains seal, minimizes tension on substrate, and reduces possibility of failure due to weak or improperly prepared substrates.
Exposed face remains virtually flat regardless of variation and changes in joint width and compression.
User friendly—no masking, mixing, priming, tooling, curing or clean-up required.
Good thermal and sound insulating properties.
Difficult to vandalize.
UV-stable and highly resistant to aging and vermin (bugs, rodents, birds, etc.)
Will not extrude from between joints when squeezed, which is a possibility with caulk or butyl-type tapes.
May be used in non-moving gasket-type applications as well as in moving expansion/contraction-type joints.

Sizes

Available compressed thicknesses:
3/32″ (10mm) up to 2″ (50mm)
Equivalent expanded thickness:
3/8″ (10mm) up to 4″ (100mm)

Available widths:
3/8″ (10mm) up to 3″ (75mm)

Download product size chart (pdf)

Movement

Emseal sealant tapes have different sealing levels at different levels of compression. For applications where movement is expected, and watertightness is required, the sealant tapes can accommodate +25% and -25% (total 50%) movement of the supplied compressed size when installed in gaps equal to the supplied size.

See compression chart below for levels of sealing at respective compression levels.

Color

AST Hi-Acrylic: Black
MST: Grey

Uses

As a water, vapor, air, sound and dust seal between metal surfaces, as well as between concrete and other substrates.
For applications requiring high temperature stability.
Ideal as a gasket tightly squeezed between joint faces that are mechanically fastened together such as lap seams.
Its resilience makes it also suitable for use in a partly expanded condition for filling preformed openings between components and where joint opening size varies due to seasonal temperature changes.
In applications where damping vibration and noise is as important as weather sealing.
As a secondary seal behind caulk.

Sealing Levels & Compression

The following indicates levels of sealing at respective installed compression levels:

Emseal sealant tape compression and sealing level chart

The Choice: AST or MST?

AST Hi-Acrylic is by volume the most widely used. Black in color as the result of it’s advanced acrylic-modified asphaltic impregnation, AST affords economy without sacrificing performance.

MST features the latest in acrylic chemistry and is grey in color. Choice of MST over AST is really a preference of the user for color and chemistry.

Installation

1. Storage and Surface Preparation
Tape should be stored in a warm dry interior location. Ideal application temperature is approx. 75°F (24°C). Expansion will be faster at higher temperatures and slower at lower temperatures.
Tip: For faster expansion in cold conditions keep the material warm before use and, if desired, apply heat from a hair dryer to installed material to accelerate expansion. Joint faces should be dry and cleaned of dirt, oils, grease, etc. There should exist sufficient depth to receive full width of the sealant.

IMPORTANT: Reels must be stored FLAT and kept compact. Should material expand in package it can still be used. Unroll material, allow it to expand, then recompress it between surfaces to be sealed.

2. Opening Reels
Only open materials that will be immediately used. Remove shrink wrap.

Cut in front of colored marking tape and pull back release liner to expose mounting adhesive.

3. Square Off Ends
Start and finish ends must be cut square. For easier cutting spray knife or scissors with mist of water.

4. Peel Off Liner
Remove release liner to expose adhesive face of tape.

5. Adhere to Surfaces
Press adhesive face to one surface. Align other surface with tape. Secure surfaces together. Tip: If needed, cut and fit small filler pieces of tape to fill panel corrugation or voids.

6. Joining Lengths
Overlap one piece of tape with another. Cut through both pieces at a 45-degree angle with a long-bladed knife. Reposition mitered faces over each other and pinch them firmly together to make a join.

Available in many sizes.
If this tape size does not return the results you desire in your specific application, ask your vendor or Emseal for other size options.

Availability and Price

Available for shipment internationally.
Prices are available directly from the manufacturer.
The product range is continually being updated, and accordingly EMSEAL® reserves the right to modify or withdraw any product without prior notice.

Limitations

Will not adhere to components that are dirty or dust covered or to surfaces coated with oils or other release agents.
Will expand to follow and fill irregular substrates within reason. Sharp corners and acute angles may need to be filled with additional filler pieces in order to ensure a proper seal.
Substrate must be capable of resisting, without bending or deflection, approximately 1.5 to 2.5 lb/in2 (10 to 17 kPa) back pressure from the tape.
UST service temperature range is -40°F to 249°F (-40°C to 120°C).
Substrate faces must be parallel and have sufficient clear depth to fully support UST.

Warranty

Standard or project-specific warranties are available from EMSEAL on request.

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