Gelcoat repair

[Pugwash 0]

Hi. I'm trying to do some minor repairs to the gelcoat with a Norski Gelcoat repair kit but the stuff doesn't seem to be hardening. Does the catalyst go off? I've had it a while.

[Guest]

I don't have any real idea but I do have a bottle of MEPK that does have a date on it. No idea why but the fact it does I found intriguing.

 

So maybe, and that is only a 100% maybe, it can go off Pug.

[Guest]

polyester based products hardener base MEKP doesn't like moisture, so even on humid days you can have issues.

 

Yes the MEKP can loose it's properties over time.

 

The other thing with repair kits is weather or not the gelcoat has a wax solution additive or not. Basically gelcoat needs wax for it's surface to harden, be it against a mould surface or a waxed overlay, or a wax solution additive.

the gelcoat surface is designed for the next glass layers to chemically bond with it, so it kind-of stays soft until the next bit goes over the top.

this can lead to all sorts of other issues when the gelcoat is too thin.

 

Being too thin could be another issue you are having when it can't develop enough energy to self promote.

 

simple test - pop the left over gelcoat out of it's mixing pot when and if it goes off. if the sides that are against the pot feel fine but the exposed side feels sticky and soft you need wax to be added to your equation.

 

or go buy flowcoat which is gelcoat with a waxed solution added for top finish coat purposes

[Pugwash 0]

So s that why I've read somewhere to cover it with cling film/glad wrap? Would that help?

[Guest]

some plastic react to the polys so it would pay to test a bit first

We've done it before with packaging tape buy sticking it to itself creating a smooth band-aid of sorts. Also using thicker stuff like you might find on a bound printed document. But always with a smear of mould release wax so to speak.

[Pugwash 0]

Thanks fng, but your advice is somewhat overshadowed by fifacoins, that just explains everything!

[Kestrahl 6]

Hi. I'm trying to do some minor repairs to the gelcoat with a Norski Gelcoat repair kit but the stuff doesn't seem to be hardening. Does the catalyst go off? I've had it a while.

 

I used some and it worked fine so it is probably to old. The only problem I had with it was it is very thin so no use for anything deep, unless you fill first with epoxy. I think Nuplex sells one that is better but that is only word of mouth.

[wheels 543]

MEKP, is Methyl Ethyl Ketone Peroxide. Please note the Peroxide part. That is the key. Peroxide is highly unstable and reactive. It reacts with both Heat and Sunlight. So storage of MEKP should be in a cool dark place. Otherwise the Peroxide starts to brake down and change what the chemical is. By the way, MEKP in greater purity is so highly unstable. It is very high on the list of Liquid Explosives. They mix in one of three other chemicals to reduce the purity to ruffly 30% to make the stuff safer. It is also a difficult chemical to get hold of in liquid form in large quantities these days, because it is so dangerous. NEVER smack the stuff with a hammer. It is like Nitroglycerine. 30% mix may not go off, but you don't want to take the risk either. It's also another reason why you get it in that red/brown coloured paste for "Car Bog".

Like anything that Peroxide is available as, great care needs to be taken with handling this stuff. Bad stuff on Skin, but it is most especially dangerous in contact with eyes, will severely burn and damage them.

Ester based Resins harden by crosslinking. It is a reaction that happens right from the get go of manufacture and continues in the can at a very very slow rate. Depending on temperature of storage, this could be as little as 12mths before a Can is completely hard. MEKP is a catalyst, NOTa hardner. All it does is speed up the process of crosslinking to a speed that makes the Resin a workable product for whatever we are using it for.

The speed of the Resin going from Liquid to Solid is determined by the amount of catalyst used. Anywhere from 0.5% for very large volume layups to as high as 3% for very small patches, scratches and fills. So for a really little fill, you may need to increase the level of MEKP used to get it to kick off.

 

Now I maybe wrong about this, but I seem to remember way back in my mind, that Norski did a gelcoat that didn't like to harden when exposed to Air. It was specifically designed to be between the Mould and the layup Resin. If you tried to use it on the outside of something, the stuff would not cure, or at least in the expected time frames. They had a different product for outside skin use. It was more a Gelcoat Putty rather than Gelcoat liquid. Gelcoat liquid has no Thixotropic properties and will simply sag and run, where as the Gelcoat putty stayed where you put it.

[Rats 28]

A handy hint when using gel coat is to use mums kitchen wax paper!

 

Fill the hole (it cannot be too deep) and then apply the wax paper and use a razor blade on its edge to draw across the top of the paper to "level" the gel coat underneath but please resist the temptation to do more than about two pulls otherwise it just gets messy

Once levelled tape down the edges and wait for the cure

 

You can get gel coat with wax in it (Flow coat)and without the wax. Without the Wax it remains sticky post cure that I think is the problem.

[Pugwash 0]

Just back from a few days away. Thanks for the replies and advice guys. I see the spam has been removed, well done Mr Moderator.

Anyway, back to the topic. I've now used all the catalyst so will need some new stuff. Anyone know of a source?

[wheels 543]

I have seen spare bottles of it at Burnsco. As much as I don't like to promote them, You don't need much so you won't get any great saving from anywhere else.