polyurethane glues

hardheart

hardheart

Joined
Sep 19, 2001
Messages
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I've read over the glue wars threads by Sando and TMickley a couple times, they did a lot of really good testing, and it seems Gorilla Glue did excellently for wood scales. But I was wondering if anyone has checked for differences with the now 'stronger & faster' Gorilla Glue, the Loctite Sumo, or another one I noticed at Lowe's, PL poly glue. The Sumo & PL are both made by Henkel, though the PL appears to be like the Gorilla Glue, the Sumo apparently dries white and expands less. I found a thread by Kerry Hampton about Sumo, but there wasn't any testing to failure (which is good, it was a nice knife in that thread)

http://www.gorillaglue.com/great.htm
http://loctiteproducts.com/products/detail.asp?catid=71&subid=184&plid=722
http://www.stickwithpl.com/Products.aspx?ID=0c90059f-3484-4981-bf6d-c0a67e878bf9
 
are any of these tested 'to age'?... my feeling is that PU is very prone to aging: yellowing (which isnt really important) and substantial changes in props over a few months/ years after curing.

Lang
 
langchop,

As a Development chemist (for Henkel), tested "to age" is always a compelling question.

What do you mean(feel) by prone to aging? And what properties do you look at(test) when evaluating?

All adhesives are affected by aging to some degree. In the development of adhesives you design in the amount of environmental factors (aging) that the adhesive can withstand and test that adhesive to failure and beyond to determine the longevity of the bonds.

When we test the aging of adhesives we do so at many different combinations of environmental factors.

This is to accelerate the aging of the adhesives, because I can assure you that many of the adhesives that are out on the market when mixed, applied, bonding the proper materials, and bonded correctly will outlive us and in many cases the materials that they bond.

So we accelerate testing to actually show that a bond will fail after 20 years of normal use, or if exposed to a high enough or low enough temperature, if sheared enough, if enough peel force is applied, and so on and so forth.

Each manufacturer has their own way of testing adhesives but in each case we torture the adhesive much more than the common consumer will subject the adhesive to.

I must reiterate, that if the adhesive is used as recommended that the bond will last much longer than the usable life of the product.

I know that this was a long ramble to maybe not answer your question completely, but if you have any other questions please let me know.
 
Sorry I'm kinda hijacking your thread heardheart. Bstach, I have developed a lot of faith in epoxy resins for various applications other than knifemaking over the years, and have a little budding interest in resins, adhesives and paints. I have found so called 'grey' epoxies to be excellent environment resistant glues, but when I have used their clear equivalents they tend to go yellow within a couple of months/ years and simultaneously soften and get rubbery. I have found this to be a similar issue with a wide range of brands, and assume this to be because there are possibly no really effective clear 'environment protectors' (UV, moisture etc) I have had similar experiences with PU products, although admittedly I have used these far less.

My 'feeling' ( I use this word because it is based on experiences and gut feel rather than raw hard facts and information!) is that an ideal glue for knifemaking would be one that doesnt shrink too much, is 'thin' enough to soak slightly into the wood before curing, has suitable strength to rigidly fill gaps and voids (ie. unlike wood glue), and not be badly effected by heat, moisture, oils and UV. Although UV should not be a big issue in such cases.

I do completely agree with you: do the prep and procedure properly, and most glues should last a lifetime. Thanks for interesting post.

Lang
 
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