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View Full Version : Polyurethane vs. Epoxy vs. Silicone vs. Acrylic - Need Adhesive for HVAC Tubing



gunDriller
2nd April 2012, 08:26 AM
I am writing to ask Youse Guys (and Gals) for Adhesive Advice.

I need to glue some pieces of metal tubing together for a home heating thing.

It's about 100 feet of tubing, a combination of aluminum, steel, and galvanized steel.

When it's done it will be about 212 degrees F on the outside, with an air intake taking in humid air ranging from 30 to 40 degrees, so I will probably get some condensation.

Most one-part adhesives say they need 40 degrees F or higher to set, though from my experience it's more like 80 degrees F for a good bond.

Since I don't have 80 degrees F to cure the assembled tubes, I need a glue that will set FOR SURE, and not let in any additional moisture - i.e., seal up ALL the holes.

The tubing is a variety of tubing that I collected at estate sales last summer - straight pieces, U-shaped pieces, 90 degree pieces, from lawn chairs, walkers, a whole variety of products that use tubing.


At the Home Depot, one of the guys was RAVING about polyurethane. I believe him, but the fumes are GNARLY until it cures, and since this will be piping air directly into my living space, I want to make sure that it is 100% cured before I use it.

Since the work area (outside under a tarp) is about 40 degrees, I was thinking, go with the 2-part epoxy.


What do you folks think ? Have you ever gotten a good 'set'/ bond from acrylic or polyurethane in cold temps ? Or bad results from epoxy setting up when it's 40 F ?

Most of my personal experience is with epoxy & silicone RTV. I have used acrylic in corporate design jobs, and have to admit that some acrylic adhesives are KILLER, but the acrylic adhesive I have access to is for gluing J-bolts to concrete, and they say it needs warmer temperatures to set up right.

undgrd
2nd April 2012, 08:49 AM
Can you provide more info about what you're doing? From the sounds of it you'll be using a boiler across a heat exchanger?

This is rated up to 180 Degrees. Should work for bonding the HVAC within the home.
http://www.americanhvacparts.com/Merchant2/merchant.mvc?Session_ID=b9d04c187b3b74e3f5d9195136 f79fa7&Store_Code=AM&Screen=PROD&Category_Code=duct-connectors&Product_Code=TPS3344

Not sure you'll be able to bond the metals together for the higher heat range. You'll probably need to weld the metal together.

zap
2nd April 2012, 08:20 PM
I'm sure you already know that you can't attach aluminum to steel, you'll get electrolysis.