RenaissanceWW Posted August 20, 2010 Report Share Posted August 20, 2010 I could probably not be lazy and go research this but asking y'all is much more fun. Why does poly glue foam? If you don't wet your surfaces is the bond weaker? I don't use the stuff much but I have had a bottle for a while and just used it on some outdoor furniture for the heck of it and this got me thinking. C'mon chemists, lay it on me. I got a 5 on my AP Chem test way back when, let's see what I remember. Quote Link to comment Share on other sites More sharing options...
LordLQQK Posted August 21, 2010 Report Share Posted August 21, 2010 I could probably not be lazy and go research this but asking y'all is much more fun. Why does poly glue foam? If you don't wet your surfaces is the bond weaker? I don't use the stuff much but I have had a bottle for a while and just used it on some outdoor furniture for the heck of it and this got me thinking. C'mon chemists, lay it on me. I got a 5 on my AP Chem test way back when, let's see what I remember. Well the foaming is part of the curing process and the chemical reaction going on. The curing process is initiated by moisture, like CA glue but poly glue takes a bit more. If you don't wet one side of the wood the curing process will be significantly slowed and in drier locations might not take place at all. Personally I hate the stuff. It is a mess to work with. It sticks to everything, especially stuff you don't want it to. It doesn't clean up well. The foaming action can actually cause joints to separate and, the last time time I checked, even tiny bubbles in the glue line causes weak points. And really it isn't even that strong of a glue. In a recent glue joint test it ranked second to last. If my memory serves correctly PVA glue was first (including TB1, TB2, and for hard core outdoors use TB3), epoxy second, then hide glue, and CA glue were all better in that order. Oddly enough, construction adhesive was the one glue that was below poly glue. LQQK Quote Link to comment Share on other sites More sharing options...
Dave F Posted August 21, 2010 Report Share Posted August 21, 2010 It's so arid here in Utah that the stuff is almost useless for me.. I'm not a fan. Quote Link to comment Share on other sites More sharing options...
thewoodwhisperer Posted August 21, 2010 Report Share Posted August 21, 2010 Just did a little digging and it looks like the chemical reaction is simply releasing carbon dioxide gas. Here's an excerpt from an article on polyurethane adhesives and it seems to apply to the chemical composition of what we know of as poly glue: An isocyanate group reacts with the hydroxyl groups of a polyol to form the repeating urethane linkage. Isocyanates will react with water to form a urea linkage and carbondioxide as a by-product. Linear thermoplastic PU’s may be obtained by using compounds with two reactive groups such as diisocyanate and diols. When polyols with three or more hydroxyl groups (i.e. a functionality of 3 or more) are reacted with an isocyanate, or when isocyanates with three or more isocyanate groups are reacted with a polyol the resulting polymer is crosslinked. The amount of crosslinking affects the stiffness of the polymer. Contrary to linear polymers, crosslinked polymers will not flow when heated. All structural adhesives are crosslinked because this eliminates creep (deformation under constant load). In reaction systems where there is an excess of isocyanate crosslinking reactions may occur. These reactions form linkages of allophanate and biuret. Polyurethane adhesives and binders By: Dr Berend Eling and Dr Chris Phanopolous, Huntsman-Polyurethanes, Everslaan 45, 3078 Kortenberg, Belgium Quote Link to comment Share on other sites More sharing options...
MarkC Posted August 22, 2010 Report Share Posted August 22, 2010 When I first used Poly glues It thought they were great--due to how powerful the bond was. But I always hated the mess they caused-- foaming, tough to clean up and tough to get off my fingers. I thought these were all good things that supported how strong the glue performed. Then the WW mags started doing comparisons and ratings and the poly glues received bottom of the barrel reports. Now I never use the stuff. I have become partial to TB3 for almost all projects indoors and outside. It has never failed me or my projects. Quote Link to comment Share on other sites More sharing options...
nateswoodworks Posted August 22, 2010 Report Share Posted August 22, 2010 The scientific reason it foams, that's easy, to piss you off. I have the same views Youngwood has, I had used it on a few projects before all the research and strength tests thinking it was the strongest, looking back at all the time I wasted removing the foam I want to go kick that gorilla's butt. There very scientific. Nate Quote Link to comment Share on other sites More sharing options...
PaulMarcel Posted August 22, 2010 Report Share Posted August 22, 2010 The scientific reason it foams, that's easy, to piss you off. I have the same views Youngwood has, I had used it on a few projects before all the research and strength tests thinking it was the strongest, looking back at all the time I wasted removing the foam I want to go kick that gorilla's butt. There very scientific. Nate LOL angry Nate (but I agree!!!) Quote Link to comment Share on other sites More sharing options...
jimmykx250 Posted August 22, 2010 Report Share Posted August 22, 2010 DOnt touch the stuff! It's like that infommercial with the caulk spreading widgit and they show the guy with caulk covering both hands! Dont touch the stuff. Quote Link to comment Share on other sites More sharing options...
samhell Posted August 23, 2010 Report Share Posted August 23, 2010 I'll tell you where polyurethane glue works well: bonding dissimilar materials. This weekend I had to glue some split PVC pipe "rails" to some particle board. The foaming action was actually a bonus in this situation. Gorilla glue worked perfect! Quote Link to comment Share on other sites More sharing options...
Chems Posted August 23, 2010 Report Share Posted August 23, 2010 I hated it when I used it. The only good use was when the items were pre-finished as it didn't bond an could be picked off, Quote Link to comment Share on other sites More sharing options...
nateswoodworks Posted August 23, 2010 Report Share Posted August 23, 2010 I'll tell you where polyurethane glue works well: bonding dissimilar materials. This weekend I had to glue some split PVC pipe "rails" to some particle board. The foaming action was actually a bonus in this situation. Gorilla glue worked perfect! OK now I am curious about what you are building?? Nate Quote Link to comment Share on other sites More sharing options...
LordLQQK Posted August 23, 2010 Report Share Posted August 23, 2010 I'll tell you where polyurethane glue works well: bonding dissimilar materials. This weekend I had to glue some split PVC pipe "rails" to some particle board. The foaming action was actually a bonus in this situation. Gorilla glue worked perfect! OK now I am curious about what you are building?? Nate And did you run out of epoxy? LQQK Quote Link to comment Share on other sites More sharing options...
samhell Posted August 23, 2010 Report Share Posted August 23, 2010 OK now I am curious about what you are building?? Nate A jig to (more) easily radius fret boards Quote Link to comment Share on other sites More sharing options...
samhell Posted August 23, 2010 Report Share Posted August 23, 2010 And did you run out of epoxy? LQQK Nope, but I only have 5 minute epoxy on hand and I need a bit more setup time than that. Quote Link to comment Share on other sites More sharing options...
Jim Rimmer Posted August 26, 2010 Report Share Posted August 26, 2010 Just did a little digging and it looks like the chemical reaction is simply releasing carbon dioxide gas. Here's an excerpt from an article on polyurethane adhesives and it seems to apply to the chemical composition of what we know of as poly glue: An isocyanate group reacts with the hydroxyl groups of a polyol to form the repeating urethane linkage. Isocyanates will react with water to form a urea linkage and carbondioxide as a by-product. Linear thermoplastic PU’s may be obtained by using compounds with two reactive groups such as diisocyanate and diols. When polyols with three or more hydroxyl groups (i.e. a functionality of 3 or more) are reacted with an isocyanate, or when isocyanates with three or more isocyanate groups are reacted with a polyol the resulting polymer is crosslinked. The amount of crosslinking affects the stiffness of the polymer. Contrary to linear polymers, crosslinked polymers will not flow when heated. All structural adhesives are crosslinked because this eliminates creep (deformation under constant load). In reaction systems where there is an excess of isocyanate crosslinking reactions may occur. These reactions form linkages of allophanate and biuret. Polyurethane adhesives and binders By: Dr Berend Eling and Dr Chris Phanopolous, Huntsman-Polyurethanes, Everslaan 45, 3078 Kortenberg, Belgium Despite the by-line at the bottom, we all know that this was Beavis and Butthead randomly picking words out of the glossary of a chemical textbook and throwing in adjectives and conjunctions here and there, right. Quote Link to comment Share on other sites More sharing options...
cosmocyb Posted August 26, 2010 Report Share Posted August 26, 2010 Ask my daughter about borrowing grandpa's Gorilla Glue to glue pictures in her photo album. That's the last time it was ever opened or will ever be opened. She had no idea what she was using, but still tried to make it my fault. Hilarious. Quote Link to comment Share on other sites More sharing options...
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