Wednesday, November 19, 2008

If you just gotta use GREAT STUFF canned foam

I've used GREAT STUFF (or the equivalent) canned polyurethane expanding foam on numerous rocket projects. Most worked out fine, but it was always messy and generally the can was irrecoverably clogged after the first use. It turns out this foam also needs moisture to cure and the rocketry community is full of horror stories about delayed curing causing bulges and worse. So, a long time ago I moved to 2-part foam. I got mine from Giant Leap, but you can get if at PML or most any composites company. It works better, you can easily measure just what you need and it lasts for years. My first batch actually went bad before I finished it but like I said, it lasted for several years.

An entry on Toolmonger tells us how to keep the nozzle from clogging so, if you just have to use canned foam, at least it won't be 'single use'. Directly from Dow:

“One-component foams as GREAT STUFF(TM) do not lend themselves to re-use. Once a can has been used and allowed to sit for more than two hours, it will seal itself shut. This is indicated on the can’s label.

“It is possible to preserve a can of GREAT STUFF polyurethane foam sealant. Insert a pipe cleaner, soaked with WD-40, into the attached applicator straw (do not remove straw from can). Leave the pipe cleaner sticking out of the applicator straw approximately 1/4 inch. This has to be done within two hours of use. The WD-40 soaked pipe cleaner may preserve the can up to 30 days.”

I love WD-40.