Using 3M Super 77

Composites One

 

I know there is a polyester/vinylester compatible spray adhesive in the US , infuzene from the advert I saw

 

Thanks, latman. The maker of infuzene, Westech Aerosol Corporation, also makes Epokz which is specifically designed to be compatible with - of all things - epoxy. Developed to hold reinforcements in place for vacuum infusion I'm pretty sure it'll work for my application. Gotta wait for them to get to work this morning to get more detailed info.

http://www.epokz.com/aboutEZ.htm

 

Composites One carries both versions also.

 

Talked to the folks at Westech Aerosol who makes Epokz and he said that it only cross-links during a vacuum infusion process; that using it as a temporary tacking adhesive during a hand layup is as potentially contaminating as something like Super 77. He also said that they had pulled it off the marked for the time being as it chemically separated in the canisters; it's being reformulated.

So much for an epoxy-compatible adhesive...

 

I searched for the right tackifier for a whole year. I did find the proper stuff that becomes one with epoxy and does not restrict the infusion flow.
Call Progress in Toronto Canada. I think it was about $20.00 or more a spray can. It is worth it to me.
If you like, I will get the product name and number of the supplier for you.
Fred

 

3m 77 doesn't contaminate the surface, nor impede the epoxy bond, again so long as it's a light dusting. There are other techniques, such as waiting until the initial prime coats of unthickened epoxy get tacky, but spray adhesive has worked for years. The PH differences between the two, insure epoxy will get penetration under the adhesive and more importantly any "extra" globs of adhesive (if applied too heavy) will remain in suspension, making the issue moot.

 

PAR,

Are you referring to 3M's Super 77 Multipurpose Adhesive or Super 77 Classic? Or, in your experience, does it matter?

I'll try spraying a light dusting on some 4mil plastic to see how light a spray I can manage.

 

I actually don't use the 3M product, preferring to use a cheaper brand. The difference between classic 77 and the new 77 is the new stuff is lower VOC.

The stuff I use is commonly called "artist's spray mount" (3M has a version of this) and has a much lower adhesive quality about it. This adhesive is designed for bonding photos into scrap books, paper to other things.

 

I will need to go back and have our lab change all their test results on the "glue" type products then.

These are worst case studies, but it shows what happens when you slightly over apply the product. Lesser amounts of glue type tackifiers would result in less loss of strength, but it will still compromise the laminate to some extent. The way I see it, if you are going to use epoxy because of its better properties, then why use something that can possibly reduce these properties.

http://www.ccponline.com/includes/PDFs/NuTack E 046-4103.pdf

http://www.ccponline.com/includes/PDFs/046-4062 and 046-4063_new.pdf

 

Wow, very interesting results. Thank you for the post. I suppose that using some slower curing epoxy to tack the glass up, then doing the lamination within the 4-6 hours time window is out of the question for the original poster?

Seems that would be the strongest way to do it, in light of this data.

 

These "worst case studies" would be precisely what I've been mentioning all along, not to do and frankly are meaningless, in as much as testing improper applications and procedures seems futile, because an experienced user will not fall into this set of conditions, making the data gathered a bit moot.

A very light dusting, is all you need to hold up moderate weight fabrics. I'm not talking about a heavy triax, but a fairly light sheathing. A quick misting with the spray adhesive of choice, just enough to hold the fabric is all that's required. Anything more is just asking for trouble. I've been using the lighter tack spray mount for both economic and contamination issues. The higher tack products such as 3M 77, can tend to spit at the surface during application, which is bothersome and potentially contaminating, but the spray mount does seem to work better in this regard.

To be honest, it isn't very often I need this technique, usually relying on a previous coating, to just get tacky and placing the fabric in it, but sometimes, often with an on site repair, I'll resort to this technique.

 

The problem is, we see these worst case situations happen frequently when you have several people placing the glass on the part or in the tool. People use a little glue to hold the glass in place, then it slips, so they apply more glue, then it moves again so they spray a little more, soon the fibers are fully coated with glue. You also have the "OOPS" factor, just a mistake from the can spitting or a misguided trigger finger. These result in small areas in the laminate that may have far too much glue and will be weaker. In over built parts this isn't as much of an issue, but in highly stressed areas or parts these sites may fail.

Even when applied in a fine mist these droplets of glue don't float suspended in the epoxy, they are bonded to the glass, core or substrate and prevent contact and bonding with the epoxy. Since there are tackifiers designed for this purpose that don't interfere with bonding or flow I can't see why someone would want to use a glue.

On gel coated parts (both polyester and epoxy) these tiny droplets bond to the gel coat and block the resin from contacting that part of the surface. Over time the difference in how the glue and resin react to the shrink during curing, heating and cooling when exposed to the weather, moisture, etc, the surface profile over these droplets can change and become a cosmetic issue, or even blister.

 

Looks like my inexperience with U.S. Composites' 635 epoxy system is largely to blame for my problems. I've used West System products for over 15 years with no problem and applied my methods with those products to the USC 635; apparently, a bad idea. Who knew that they want the hardener in the pail first, that the resin and hardener need to be between 80 and 110-degrees before you start mixing for at least five minutes? Not me...

Luckily, I have newly developed skills at removing fiberglass that seems to be well-epoxied but may not be totally cured due to my poor methods. Tomorrow is a new day...