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ke6cvh

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Posts: 597
Reply with quote  #1 
Hello group,

  I'm starting two topics today, this is the first.  I saw an old topic regarding "what is your favorite polyurethane" but it did not focus on the expensive (about 60 dollars a gallon) two part polyurethanes that mix like one would be mixing epoxy.  I ran across this stuff when searching for abrasion resistant properties of various plastics with the assumption UHMWPE was king (Ultra High Molecular Weight Polyethylene).  Yes, UHMWPE is one of the strongest fibers on the planet but I started to do some in house testing of different diameters of monofilament fishing lines compared to braided HPPE (High Performance Polyethylene) line at same diameter.  The mono filaments blew it away even when I tested simple weed trimmer line it was far superior.  The problem is UV is a serious enemy of nylon while not being so for UHMWPE.  So it turns out that polyurethane is also susceptible to UV but can be limited by adding pigments and other additives.  We did a restoration some time back of a circa 1910 Singer 16-88 and used an in house cold cure japanning that consisted of asphaltum that I can buy by the kilo melted with a heat gun into spar varnish.  Spar varnish is too rubbery for my taste.  I wanted to try a polyurethane.  Back to abrasion resistance the "good stuff" that is likely the 2 part and expensive stuff is used by skin on frame kayak builders over the cloth apparently.  The link below shows the best types have abrasion resistance slightly higher than D2 tool steel and also better than UHMWPE.  I've included two of their links.  I'm going to contact these folks and see if I can get a 2 part with a black pigment (maybe a black gloss if that is possible).  Hardware store stuff is not the same as it has solvents and those can be evaporating for weeks.  Let me see.....a 2 part polyurethane that has better abrasion resistance than D2 tool steel and dries quickly not releasing solvents for weeks?  Sounds like an awesome possibility that I could put consecutive coats built up over a SM head.  Maybe even impervious to the occasional zipper drug across it...unlike my cold cure japanning experiment that looked good but easily abrades if one runs a zipper across it.  Links below.  Now I need to get ahold of these folks and ask some questions if they can provide a special black sewing machine recipe.  Best regards, Mike Kendall  https://gallaghercorp.com/polyurethane-abrasion-resistance/          https://gallaghercorp.com/white-papers/uv-stability-polyurethanes/
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Deb

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Posts: 297
Reply with quote  #2 
Just kinda thinkin out loud here...
How would you apply this? For full restoration you could dip the whole machine maybe or use a spray gun, but I was thinking it would be great protection to put on the beds of the machines I use all the time. If a brush was used would it leave marks? Could it be applied over other finishes or would they need to be stripped first? 

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Deb in WI
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ke6cvh

Senior Member
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Posts: 597
Reply with quote  #3 
OK, like I said I found it searching for abrasion resistance and kayaks (we completed a 2 person strip built kayak when we were in Japan).  We used spar varnish (bad compared to this).  A quart (or liter I'm a little confused on the description calling it a gallon) is 60 dollars after the thinner so I correct here.  It must be applied in thin coats or it does not work properly.  Description from the boat builders say with regular polyurethane if you run a piece of metal across it then it scratches.  If you run a piece of metal across this stuff it does not.  The "cons" in description talk about precious liquid being wasted in the dispenser system so I guess they are saying move it into a better container that dispenses better.  One 60 dollar purchase did 4 applications on a complete kayak so you get what you pay for.  It can be applied with a quality brush to answer.  Likely I cannot get this overseas but if in USA I'd be buying it 100 percent for sure on some restoration and important projects.  Here is a link for the boat builders stuff from a store called "One Ocean Kayaks" which is a very reputable supplier.   http://www.oneoceankayaks.com/Wshophtm/Shop28.htm
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