Which expand foam do you guys use for making the plug? I used the red can but it’s not rigid enough to sand…
http://greatstuff.dow.com/greatstuff/diy/products/gc.htm
or am I looking at the wrong stuff?
you should use a two part system, the can stuff is no good.
http://www.jgreer.com/Foam%20Page.htm?gclid=CJLVq8-D9JkCFdxM5Qod_n4nRg
I have the 2 parts foam, but it’s hard to use for just fill in the gaps between the foam boards.
o, do you need to use foam? you could always use other materials such as clay, fillers, or fiberglass over your plug to close the gaps.
Stay away from the canned stuff, and use the 2 part mixture. Just wait until it starts to thicken before pouring.
And try not to mix materials. Use foam to fill gaps in foam, keeping density consistent too. Different materials will have different CTE’s and will transfer heat at different rates. No good for anything that’s curing on the surface, such as coatings, paints, or resins.
I worked at a business that manufactured urethane foam liquids. It was amazing how the chemist on staff could change the forumula to achieve different densities and stiffness of foam. I think each manufacturer’s finished specs of their product is different somewhat.
If you guys use a lot of foam or want another supplier try contacting General Coatings in Fresno California. They may sell it by the 5 gallon pails, not sure though because most of it is packaged in 55 gal drums for shipping. If you want you can ask to talk to the chemist to see what can be done to make the foam more ridged/hard. It was great working there and talking to this old guy, very very knowledgeable about his field and just a nice guy to talk with.
Also I know heating the A and B components makes a difference in the quality of the mixture or finished foam product. When we injected foam into our cold storage doors during mfg, we had drum heaters for our A and B barrels.
For big shops that do a lot of large plugs… Instapak ( or InstaPack) company makes a heated dispensing gun that sprays out the mixed components. We used ours at one shop for foam packaging application. The gun/system would work with any two part urethane foam. Also foam roofing companies use a similar mobile set up… pull the trigger and go. Messy to clean up after but acetone works well for that.
I agree about the hardware store aerosol can foam… it isn’t that great because it does not get hard.
Another tip is when mixing A/B foam, use a drill and a paint mixer to mix it.
You will get much better consistency in terms of bubble size (less random large bubbles) and color.
Another tip is to make sure the foam has somewhere to expand. This gives a more consistent density.
Even when pouring the mix into a deep recess, the foam at the bottom will usually be higher density because it can’t expand as much due to the weight of the foam above. The stuff on top will usually be lighter since it can easily expand. Tricky stuff.
There’s 4 components for the foam to work, A & B, plus oxygen and moisture in the air for it work properly.