sikaflex, silicon - how do you stop the nozzle bunging up?

Burnham Bob

Burnham Bob

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I tried a long screw down the nozzle, but that was no good. Is there any sensible way of making sure you can use what's left when the nozzle and the first 10mm in the tube has set? Or am I going to get messy digging it out?
 
It always surprises me how many tubes of various sealants do not have screw caps for the nozzle. I seal them with a piece of insulating tape, which is reasonably effective, but if you don't use the tube for a few months, then it will star to solidify in the tube as well. If it's just the nozzle, a skewer is effective in clearing it. If the tube has bunged up - forget it!! It's all part of the manufacturer's ploy to sell more sealant!
 
Burnham Bob said:
I tried a long screw down the nozzle, but that was no good. Is there any sensible way of making sure you can use what's left when the nozzle and the first 10mm in the tube has set? Or am I going to get messy digging it out?
Click to expand...

If you put part used tubes in a freezer shortly after using them and keep them there the nozzle doesn't bung up and they last for ever.
 
As I've never found screw tops on nozzles particularly effective, I've found taking off the nozzle and inserting a piece of polythene sheet (not bio-degradable) between nozzle and body, kept in place by the nozzle-screw, to be the most effective. Silicone lasts 5-12 months, polyurethane about 15-18 months and polysulphide and acrylics almost indefinitely.
Usually best to have several spare nozzles but, if the sealant has completely cured, using a bike spoke to force it out.

As few on a boat have a freezer the choice is limited (as well as being death for acrylic and, probably, polyurethane).
 
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charles_reed said:
As few on a boat have a freezer the choice is limited (as well as being death for acrylic and, probably, polyurethane).
Click to expand...

If you cover the nozzle when you have finished using it and take it home and put it in the freezer at the end if the day that's good enough to preserve it. No good for an on-board supply for most of us I agree. I have done this with all types of sealant and none has died or shown any performance degradation after storing at low temperatures. They would receive this temperature in transport and storage in cold parts of the world anyway. -18C is only cold for us in soggy UK; it's a balmy winter's day for the Canadians.

Freezing part used tubes of sealant is not something I have come up with - it's a tip that has been doing the rounds for yonks. I have seen boat yards do it too.
 
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I don't know if it is always an effective substitute for Sikaflex but CT1 doesn't seem to suffer from this problem. I used a new tube of it around a year ago and a couple of days ago I needed to use it again and it was fine. The nozzle comes with a screw-on cap.
 
AngusMcDoon said:
If you put part used tubes in a freezer shortly after using them and keep them there the nozzle doesn't bung up and they last for ever.
Click to expand...

+1 for freezing. It really does work. It only takes a couple of minutes before they can be used as they don't become solid.
 
AngusMcDoon said:
If you cover the nozzle when you have finished using it and take it home and put it in the freezer at the end if the day that's good enough to preserve it. No good for an on-board supply for most of us I agree. I have done this with all types of sealant and none has died or shown any performance degradation after storing at low temperatures. They would receive this temperature in transport and storage in cold parts of the world anyway. -18C is only cold for us in soggy UK; it's a balmy winter's day for the Canadians.

Freezing part used tubes of sealant is not something I have come up with - it's a tip that has been doing the rounds for yonks. I have seen boat yards do it too.
Click to expand...

Yes, but for someone who livesaboard for 6-12 months in the Med at a time it's not an option - is it?
 
Burnham Bob said:
I tried a long screw down the nozzle, but that was no good. Is there any sensible way of making sure you can use what's left when the nozzle and the first 10mm in the tube has set? Or am I going to get messy digging it out?
Click to expand...

I take it sikaflex cartridges do not come with a cap to fit on the nozzle.

When I was working and could get hold of them I used to fit a rubber policeman on cartridges not supplied with a cap.
 
You can buy spare nozzles with or without screw caps on ebay. Pity there aren't any caps to put directly onto the tube. I suppose a stock of spare nozzles and the suggestion to put poly sheet over end held on with a new nozzle would work.
 
>If the tube has bunged up - forget it!!

I dig out the wide end of the nozzle with a screwdriver then at the small end push it out with a small screwdriver. I've always found the sealant in the tube is fine. Also all the sealants I've bought have cap but it does nothing to stop the sealant in the nozzle setting.
 
I take off the nozzle and put some plastic (part of a carrier bag maybe) over the end and then screw the nozzle back on. The silicon or whatever in the nozzle goes hard but the rest of the tube stays ok.

I've also found that ct1doesnt seem to go hard.
 
I find cling flm works better than polythene - is it less permeable?
Putting in freezer - or even jst fridge - does help.
PU40 lasts much longer than Sikaflex as well as being less than half the cost.
 
If I understand correctly nearly all PU based sealants cure by using water vapour from the atmosphere.
I've always assumed that once this process starts at the end of your nozzle there is nothing you can do to stop it curing the first bit at all cos the water vapour is in there reacting away.
So by sealing it up you are limiting the moisture getting in and slowing or stopping the reaction.
I guess freezing it slows the reaction also.

Just thinking out laud.................
 
I tend to put insulating tape over the end of the nozzle.
Tends to work if you are using the tube again within a week or so.
If the nozzle is congealed, I change to a spare nozzle.
 
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