Sikaflex help!

[rph142]

I was making great progress sikaflexing my canopy until I pulled the tape line, which then smeared the fillet onto the canopy, which I then attempted to touch up only to smear it even worse. My question is will sikaflex stick to unprimed canopy? How hard is it to clean up a smeared edge? The primer line is really nice, but the adhesive sort of smeared over where I tried to touch it up.

 

[BH1166]

Leave it, let it dry. No primer no bond on glass. Give it a day or so. Rub it off gently. Mineral spirits are safe to clean with after drying. Good luck.

 

[dmattmul]

Agreed

It has a difficult time adhering to non-primed surfaces especially if it has not been scuffed. Just let it fully cure and it will “roll off” unprimed and unpainted surfaces.

I’d try rolling it off before introducing any hydrocarbon solvents. They are very unpredictable.

 

[Jetmart]

If you do choose to use a solvent AP Airplane Plastics, who make the canopies, recommend Mineral Spirits to me to get bad tape glue residue off. From their website:

How should I clean my canopy?

Use cleaners specifically for acrylic. A damp cloth or an air blast will clean the dust away. To achieve the best results use fore and aft motion instead of a circular motion. To clean dirty acrylics use plenty of water and non-abrasive soap or detergent. All-cotton flannel can be used for drying. Never use aromatic solvents such as acetone, benzene, carbon tetrachloride, lighter fluid, lacquer thinners, gasoline, window sprays, concentrated alcohol, ketones or scouring compounds. Avoid using cleaners with ammonia, such as 409. Grease, oil or tape residue may be removed with kerosene, white gasoline, naphtha or isopropyl alcohol (Do not use isopropyl alcohol on extruded acrylic). Mineral spirits is our favorite. Wash approved solvents off of canopy with Dawn dishwashing liquid or equivalent and water followed by a clear water rinse. To prevent water spots, blow dry with compressed air or wipe dry with soft cotton flannel.

 

[Desert Rat]

You're good. Just let it dry. It won't stick hard to the canopy if there's no primer under it. Once it dries you can peel it off with your fingernail.

 

[rph142]

Awesome news…I’ll step back from the ledge.

 

[wirejock]

Sika

Awesome news…I’ll step back from the ledge.

It rubs off if there's no primer. Like that booger stuff on the back of junk mail credit cards. Don't attack it till it's cured. Start with rubbing then move up to more aggressive methods.

Yea. You have all rolled that credit card booger between you fingers. You know you have!

 

[PhatRV]

I cut off the wood coffee stirrer stick into a shape of a utility knife and use that shape to scrape off the excess Sika.

 

[wawrzynskivp]

Rigger's Tip

Lots of times when the wet goop needs just a little touch up, we take a dab at it and things just snowball.

The tips is to do your touch ups wet. Whatever appropriate solvent on a tool or a gloved finger can do wonders for smoothing things out. Of course you can over-do it, but if you are quick and strategic you can make some really nice improvements.

Works for any caulks like Sika (paint thinner), waterbased stuff like latex, even epoxy fillets can take some help using denatured alcohol.

Folks that do this professionally often use a spray bottle of the solvent to set a slippery layer for smoothing.

Just don't go at it with anything dry.

 

[dmattmul]

SIKA adhesion no primer

Last year I did some adhesion testing with SIKA (Also Silpruf) to better understand the adhesion qualities of each. With primer and scuffed at 1/8-inch SIKA thickness the adhesion was almost impossible to break the bond. Using 1/4-inch plexi ended up breaking the plexi with a one square inch bonding surface. Without primer was able to separate the SIKA from the plexi not easily but doable. (It was scuffed pretty well with 60 grit)

What was almost more interesting is at 10 days in my workshop in the garage (Over 80 F most of the days) the SIKA after seemed to give off a fairly strong odor like it was not completely cured.

I also did some freeze testing to better understand adhesion qualities. Both Sika and Sil performed very well.

 

[PaulvS]

Last year I did some adhesion testing with SIKA (Also Silpruf) to better understand the adhesion qualities of each. With primer and scuffed at 1/8-inch SIKA thickness the adhesion was almost impossible to break the bond. Using 1/4-inch plexi ended up breaking the plexi with a one square inch bonding surface. Without primer was able to separate the SIKA from the plexi not easily but doable. (It was scuffed pretty well with 60 grit)

What was almost more interesting is at 10 days in my workshop in the garage (Over 80 F most of the days) the SIKA after seemed to give off a fairly strong odor like it was not completely cured.

That is interesting. What were the results for the Silpruf? I understand that the Silpruf may not require a primer. (apologies for slight thread drift!)

 

[dmattmul]

Silpruf results

That is interesting. What were the results for the Silpruf? I understand that the Silpruf may not require a primer. (apologies for slight thread drift!)

I was slightly concerned as you mentioned the Silpruf did not use a primer. I did not have access to an Instron as in my previous life but my estimate Silpruf proved better adhesion than non primered Sika but not quite what Sika with primer provides. Based on Glassairs experience and the fact Silpruf provided a fairly good bond both at room temp and -25 F used Silpruf. If I ever need to replace a window I feel I can do this a little more easily with Silpruf. Sika would be very difficult which is obviously a good aspect.

 

[drinkwater]

I can answer why the sikaflex may not have cured in a warm shop. Sikaflex, as with most polyurethane sealants (and many silicones as well) is moisture cured. The cure process absorbs atmospheric moisture. Hot and dry /low humidity conditions can adversely effect the cure. In hot dry conditions it is sometimes advisable to mist the sealant with water to help with the cure (and some manufacturers include this tip with their install manual) . From the sikaflex datasheet:

Sikaflex® Construction Sealant is a premium grade, moisture-cured, 1-component, polyurethane based, non-sag elastomeric sealant

PS. As a rule of thumb, I would stick with the polyurethane base over silicone. Silicone is a contaminant that nothing sticks to, except more silicone. It is extremely difficult to remove, there are no practical solvents which dissolve it, and only a few will soften the material. It's really easy to contaminate other surfaces with an invisible smudge that can ruin a paint job. For repair, you can only go back with more silicone, sika won't stick to silpruf.

Edit 2 - this is from the Silpruf TDS:

The cure rate of this product is dependent upon temperature
and the availability of atmospheric moisture. Under Standard
Conditions (relative humidity of 50 ± 5% at an air temperature
of 73.4 ±2°F [23 of ±1°C]) this material can attain a cured
thickness of 2-3 mm per 24 hours (assuming ample access to
atmospheric moisture). As temperature decreases, the cure
rate slows down (and vice versa). Low moisture environments
will also reduce the cure rate.