Installation Guide For Mindy Silicone Structural Sealants

This guide cannot be considered a comprehensive quality assurance for all situations as construction projects may vary.

Drawing Review:

Structural glazing industry guidelines (ASTM C1401) suggest that drawings and details are to be reviewed by all parties involved in the manufacture of an SSG system and for each building project.All silicone structural glazing applications using adhesive/sealants must be reviewed on a project specific basis.The maximum design stress on the structural silicone sealant shall not exceed 20 psi for materials have a minimum strength of 100 psi. This shall provide a safety factor of not less than 5:1. structural silicone sealant shall have a minimum modulus of elasticity to limit the movement of the joint width to no more than 25% of the glass thickness of the outboard lite. The recommended minimum structural sealant bite and thickness shall not be less than 6mm. The structural sealant bite to thickness ration shall be between 1:1 and 3:1. Structural sealant thickness controls the allowable movement of the glass unit within the frame.

Adhesion Testing:

Evaluating the adhesion of its products to materials that are representative of those to be used on the project is necessary. Upon completion of this testing, decide product selection, surface preparation, and primer recommendation (if required). All samples submitted for testing should be a minimum of 200mm (8 in) in length. For example, for aluminum extrusions, supply one 200mm (8 in) sample for each sealant to be tested. For glass, one standard 300mm by 300mm (12″ by 12″) sample is sufficient.

Compatibility Testing:

Incompatible glazing accessories (gaskets, spacers, backer materials, setting blocks, etc.) can lead to sealant discoloration and/or loss of adhesion to the substrate. To ensure compatibility, should test the compatibility of project specific accessory materials with Mimdy’s silicone sealants before application. For each sealant to be tested, supply 100 mm (4 in.) minimum length of the gasket, spacer or setting block.

Non-Stain Testing:

If natural stone is being used on the project, it is necessary to test and evaluate the performance of its sealants to determine if fluid in the sealant has the potential to migrate into porous substrates such as granite, marble, travertine and limestone.

Skin-Over Time / Elastomeric Test:

For one-part sealants, a skin-over and elastomeric test should be performed once per week and on every new lot of sealant used. The purpose of the test is to check the sealant’s working time and to ensure the sealant cures fully. Any great variation (excessively long times) in the skin-over time may indicate an out-of-shelf-ife sealant.

Test procedure:

1.Spread a bead of sealant into a 3mm film on a polyethylene sheet.

2.Every few minutes, touch the sealant film lightly with a stick.

3.When the sealant does not adhere to the stick, the sealant is said to have skinned over. Note the time required to reach this point. If a skin has not formed within 2 hours, do not use this material and contact your Mimdy distributor.

4.Allow the sealant to cure for 48 hours at 23℃ & 50% RH. After 48 hours, peel the sealant off of the polyethylene sheet. Stretch the sealant slowly to see that it has cured to an elastomeric material. If the sealant has not cured correctly, do not use these sealants.

5.Record the results in the project log book. This testing must be completed and results recorded, retained and be available for review upon request.

Shelf Life and Storage Conditions:

One-component/Two-component(base and catalyst)structural sealant:12 months from the manufacture date stored in cool & dry place below 27 ℃.

Mixing, Pumping and Dispensing

Two-component structural sealant:Before starting sealant application using two-component pumping/mixing equipment, a ratio check of the weight of Part A to weight of Part B is to be done to assure proper mixing ratio. Most variable ratio pumping equipment provide a set of valves that can be opened. Hold a disposable cup underneath each valve outlet, open the valves for a set time (10 seconds, with a minimum of 3 strokes of both the base and catalyst pumps). The collected samples of each material can now be weighed to determine the dispensing ratio by weight. The acceptable range for the volume ratio of base-to-catalyst for Mindytwo-component structural glazing sealant is 9:1 to 11:1.

 Butterfly Test

2-component structural sealant must be thoroughly mixed by the static mixers in the pumping equipment. The mix should be checked periodically during production, and must be checked after the mixers have been purged and production is just starting. To check the quality of the mix, the following “Butterfly” test procedure may be used:

1.Have pumping equipment in a mode which is “ready” for production.

2.Lay out a piece of paper (approx. 200mm x 500mm) and dispense a bead of silicone (approx. 15mm deep x 18mm wide x 40mm long) down the center of the paper.

3.Fold the paper in half so the silicone is in the center of the crease and push on the bead so the silicone is flattened out to approx. 3mm to 6mm thick.

4.Properly mixed material should have no white streaks of unmixed base. If streaks are present, then more material must be pumped through the lines to improve the mixing quality. If the sealant is a consistent black color, the sealant is properly mixed and ready for use. If gray or white streaks continue, equipment maintenance may be needed. Cleaning or changing the mixing system, dispensing hose, dispensing gun, or ratio system ball check valves can often correct this problem.

Snap Time

The ratio at which the silicone is mixed is extremely important. The quantities of part A and part B should be closely monitored to ensure the proper amount of each component is used. The following procedure will give an indication of the cure rate of the silicone:

1.Fill a small cup with the mixed silicone approximately 3/4 full.

2.Place a sick in the center and to the bottom of the cup.

3.After 15 minute and 5-minute intervals thereafter. Pull on the sick and release. If the sick snaps back, the sealant has reached its “snap time”.

4.If the sealant does not tear within itself (cohesively) when the stick is pulled out (sealant is still semi-liquid and stringy), the sealant has not snapped.

5.The snap time will vary depending on the ratio of base to catalyst. Atmospheric conditions affect the snap time slightly. A snap time varying more than 15 minutes from what is expected may indicate an equipment or sealant problem. Consult Mimdy and the pump manufacturer before continuing to use this material.

Installation

1.Surface preparation:Joint surfaces must be clean, dry, dust free and frost free.Sealants may not adhere or maintain long-term adhesion to substrates if the surface is not prepared and cleaned properly before sealant application. Using proper materials and  and cleaning procedures is vital for sealant adhesion.

2.Cleaning materials:  clean, fresh solvent; clean, white cloths free of lint or other lint-free wiping materials; primer (when required).

3.Cleaning procedures:  Remove all loose material (such as dirt and dust), plus any oil, frost or other contaminants from the substrates to which the structural silicone will be adhered. Do not use detergent to clean the substrate as residue may be left on the surface. Wet one rag with solvent and wipe the surface with it, then use the second rag to wipe the wet solvent from the surface before it evaporates. Change the cleaning rags frequently, as they become soiled. If cleaned areas are again exposed to rain or contaminants, the surface must be cleaned again.

4. Primers:  Mimdy Silicone Structural Sealant will bond to many clean surfaces without the aid of a primer. For difficult-to-bond substrates, the use of a primer or special surface preparation should be evaluated.

Tooling Sealant: Masking tape should be used to keep excess sealant from contacting adjacent areas. Apply the sealant in a continuous operation using a caulking gun or pump. A positive pressure, adequate to fill the entire joint width, should be used.Tool the sealant with firm pressure before a skin begins to form (typically 10 to 20 minutes). Sealant is tooled into the structural joint to ensure it wets out and contacts both sides of the joint and the spacer without any voids in the sealant joint.Remove the masking tape before the sealant skins over (within about 15 minutes of tooling).