In the freezer
I was told by some construction workers here that a tube of sikaflex pro will generally last for two weeks before it's starting to harden in the nozzel. When you put it in the freezer, its storage life seems to improve far beyond what one would expect with the Arrhenius Equation, where a halving in reaction rate is expected for every 10 degree celsius reduction in temperature. I suspect this is because these polyurethane sealants react with water to cure, so if that water is locked down in crystalline form because it is frozen, the polyurethane simply can not cure (I'm an engineer not a chemist, so take it as you will). The same seems to apply to the 3M Firebarrier 2000+ that we use on the firewall. Because these silicon sealants also need to react with moisture, I have put an opened tube in the freezer, then three months later pulled it out and it's as good as new. Both the sikaflex pro and fire barrier 2000+ seem to work great straight out of the freezer without any thawing time required. The real key is getting them back in there as soon as possible once finished so that the reaction in the nozzle doesn't begin. This has resulted in a tube of sikaflex pro lasting me more than six months. I just stick a smooth plug (nail etc) in the end of my tubes then wrap a small amount of duct tape around it just to hold it in place, and into the freezer they go.
Tom.
