How do marine sealants ‘go off’?

[fredrussell]

I’d like to decant some CT1 into a 200ml syringe for using small amounts sparingly. If such a sealant comes into contact, albeit briefly, with air as its transferred to the syringe, will this begin the curing process? The reason I ask is that when sealants are used to seal, for instance, some deck hardware, most of the sealant is not in direct contact with the air and yet it goes off fine. I assume it cures from the outside in. Will the brief contact with air as CT1 enters syringe have the same effect? Nozzle of syringe will be kept air-tight, obviously.

 

[pvb]

They usually require the presence of moisture in order to cure. Air usually contains moisture.

 

[TQA]

I know nothing about your particular sealant but found out the HARD way that the only way to keep sealants like 3M 4200 in the tropics for any length of time is to keep it in the fridge in a ziplock bag.

 

[vyv_cox]

I have not used CT1 but Stixall, which I believe is very similar, lasts well when sealed with a cap. I have used the remnants of a tube today, still flowing but with increased viscosity, at least two years old. I find that squeezing a little into the cap before screwing it onto the nozzle helps to keep it alive. The same technique helps with Puraflex 40 but two years is more than I have managed.

 

[thinwater]

As others have stated, polyurethanes use water as the curing agent. It doe not take much. Stixall is a polyurethane/silicone blend.

The fridge is the best place. You should be able to get at least 1 years, even if the tube is opened and used repeatedly. The low temperature slows the reaction, and the cold air holds very little water.

As for my tool box, I keep a small roll of butyl to have handy. It does not go off, but it's not for everything. Handy, though.

 

[Mike k]

I think the sealant people are missing a trick, most people waste lots of 'gone off stuf'f when all they needed in the first place was a small amount to do a little job. I would buy 25ml tubes or something like it and even pay a premium.

 

[alahol2]

I reckon there's a market for a decent air tight sealing cap that fits sealant cartridges. I guess it's not an ongoing market place though.

 

[thinwater]

^^ I'm not sure it is all about an airtight cap. No matter how they are sealed, the process has started from water that was absorbed, it seems. Maybe if you discharged a little more before sealing. But cold works. Jute negotiate with the wife for room for a freezer bag. I have a separate small beer fridge, and that works out fine (the sealants are in the veggie drawer).

 

[Kelpie]

Ct1 stays useable for many weeks, and comes with a screw on cap. Far better than Sikaflex in this regard.

 

[duncan99210]

I remove the nozzle and put cling film over the end of the cartridge, then replace the nozzle. Returning to the thing up to a couple of months later it's an easy job to remove the plug of set sealant from the nozzle whilst the stuff in the cartridge is usually fine. Alternative is using the smaller Sikaflex tubes but you really do pay a premium price for them.

 

[fredrussell]

Well, I’ve filled a syringe and put it in the fridge after use. Hopefully will last a while. The syringe made using a small precise amount very easy - far better than using the cartridge and gun in this respect.