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DIY Boot Foaming

post #1 of 6
Thread Starter 
I have some Technica Icon Carbon boots that I bought that have brand new liners which have never been foamed. The components of the foam are bottles of diphenymethane 4,4 diisocyanate; and polyol. The bottles are marked "best if used before 2/02" and I'm concerned that the DMI may likely be past its prime and would produce poor quality foam. I did a little research on the process and I see there have been several patents regarding optimizing properties of injectable foam and reducing emissions from the process. There are methods of blending tolulene-based agents (TMI's) with DMI, and there have been introduction of different surfactants and catalysts which can change the character of the end-product (http://appft1.uspto.gov/netacgi/nph-...DN/20050043425)

To cut to the chase, Great Stuff is injectable polyurethane foam and contains more additives, has a ether-agent catalyst (http://www.dow.com/PublishedLiteratu...omPage=GetDoc), and the obvious advantage of a propellant for injection vs the Ergo-Foam method.

So the question is, for either a chemical engineer out there or someone who has tried this approach, which product is the best choice between the window gap version which cures flexible; or the standard gap-sealer version which cures rigid? (I'm assuming the triple-action version for huge gaps would just make too huge an oozing mess).

The cure time is about an hour. I plan to inject the lateral aspect of the liners initially, ski in the boots, and then later inject the medial pockets and the tongue. I'll probably experiment with an old pair of boots first with the two different versions to see what happens...

Also, since I'll have the advantage of propellant, it might be better to seal one end of the pocket (after removing the outflow hose) and just inject the pocket using the straw which comes on the can of Great Stuff while withdrawing the straw, then duct-tape the opening before it all expands, place the liner in the shell, foot into the liner, and wear it for an hour.

There are canned/spray PU foam products available other than Great Stuff which might be better suited...suggestions? DAW
post #2 of 6
Thread Starter 
OK, I'll respond. I bought a pair of Lange boots from Goodwill and made razor-blade incisions into the liner, one medial; one lateral, and injected PU foam...the flexible-curing window type laterally and the large gap-filling version medially. I wanted to leave some wiggle-room for compression/pack-out of the foamed liners so once I injected the foam and inserted the liners into the shells, I placed my BARE foot into the boot, cinched the buckles, and prepared to walk around for an hour or so while it all cured...however, within about 10 minutes I noticed a creepy feeling on the skin of my foot as the PU foam leached through the permeable "barrier" of the boot liner interior. Killing time, I began reading the product warning label with interest. So I peeled the boot off and in spite of washing my foot vigorously, I noted that an hour later two of my toes were bonded together pretty tightly (Great Stuff!).

I cut the liner apart later to see how the cured PU foams compared. The flexible-curing Window Gap version seems useless as it is easily compressible, has low elasticity/rebound, and packs out rapidly...but the black can, Wide-Gap, version looks promising. It cures firm but not hard, it maintains good elasticity and rebound and is aggressive while filling voids when first injected and activated. I anticipated the opposite result so I'm glad I tested. I pulled the factory-provided fill tubes out of the Tecnica Ergo Foam liners. No great mystery as to why they were prone to failure, they have retaining batons through the ends of the fill tubes that essentially block the flow of the foam by 1/3. A flawed design. The out flow tubes seem more well thought-out, but that's moot since the foam likely won't arrive there.

I'm going to inject the Black-Can Great Stuff into the liners after packing them a bit and maybe apply some low suction to the outflow tubes so that I know the foam has permeated all the crannys...and wear plastic bags on my bare feet...DAW
post #3 of 6
Hello drdavidmom,

So how did the foaming go?

I ask as I have very high volume feet so when I tried the thermoformable liners they add too much volume = pain...so I have been considering foaming as the solution.

post #4 of 6
Thread Starter 
I haven't tried it yet. I got some advice from Jeff and I got, erh, cold feet re doing the foaming myself. It's expensive to have it done by a boot shop so I may still go ahead on my own but I need some sort of suction applied to the outflow hoses (maybe I'll hook up a vacuum cleaner to a fixed-size orfice) to ensure the foam fully circulates/fills the space in the liners. I'll post it if I do it. DAW
post #5 of 6
You'll need some pretty powerful suction, I'd think. Will a shop Vac do?
post #6 of 6
Hello BigE,

O&P folks use a 2 litre cola bottle to provide the vacuum when doing full body casts so I think a shop vac is way too much!

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