Does Flow Coat have a use by date

[JamesSmith]

Hi guys I work for Anglian Water, this time of the year we work on our fishing boats, patching and fixing cracks.
We had some flow cost left over from April, so used it last weekend and it seemed ok.
But I came in to work the other day to find a colleague had put catalyst in the the paint I was using, claiming it's out of date and only lasts 3 months.
Due to this I was unable to complete any work on the boats.
Is this right as it seemed fine to me and we have had to buy more which hasn't been delivered due to the xmas craziness.

 

[Mr Efficiency]

You mean Polyester flow-coat ? Put the catalyst for the flow coat into some paint ? Not following the reasoning there. If it was "going off" OK, I can't see any reason not to use it.

 

[JamesSmith]

Hi, yes it was going off fine I have a completed boat where the flowcoat has gone off.
So does it have a use by date at all ?

 

[Mr Efficiency]

Well, I have used resin that was years old for small jobs without incident, but for high value projects I would prefer not to take that risk, all organic substances break down over time, but I doubt a few months would make that much difference. I bought a couple of drums to make some pouring foam and the vendor emphasised it was very fresh, which presumably was seen as an advantage, but realistically a lot of stuff stays on the shelf for more than a few months. Perhaps look at the resin container for use-by dates for reassurance.

 

[JamesSmith]

Cheers we had some in cans which it was decanted from a large vat so the cans do not reflect what’s in them. Because of cosh we are his buying our own cans with the relevant info on so I’ll check them out when we receive them. Thanks for the info it’s been helpful

 

[ondarvr]

All polyester resins have a shelf life, typically it’s three months, unprompted resins are longer, normally six months.

This doesn’t mean that on the first day of the fourth month it’s bad, only that the company will warranty it to still be in spec for that period of time.

All resins begin to change right after being blended and placed in the drum, normally the gel time drifts out longer and the viscosity becomes lower. The shelf is the length of time resin will reliably still be in the window it was adjusted to be in (gel time and viscosity).

 

[ondarvr]

The longer the resin sits around the longer the gel time may drift out, this can be very important in a production environment, and less so for a different application or use.

At some point the resin may not cure well, or at all, so using old resin can be risky.

There is no exact time frame when a resin becomes unusable, it has to do with the chemistry of that exact resin and batch, plus how it was stored.

I’ve had resin go bad in a few weeks, and others are still usable a year or two later.

The older resins shouldn’t be used in critical applications though, there’s no way to easily tell whether the physical properties of the cured part will be what they should be.

 

[Mr Efficiency]

The older resins shouldn’t be used in critical applications though, there’s no way to easily tell whether the physical properties of the cured part will be what they should be.

Being flow-coat, it would be easy enough to just test a small sample, and after a few days, to see if it is adhering properly, has set-up hard etc. I guess in a professional shop situation, that might not be an option, to wait, but I think for most amateur uses, it is worthwhile to do that, and the consequences of less than perfection with flow coat are not that great.

 

[ondarvr]

The problem is even though the material appears to get hard and tack free, the physical properties may be low.

Water resistance, crack resistance, UV resistance and the bond to the substrate my be reduced significantly, but not show any signs of it for a time.

This doesn’t mean it can’t be used, just that the person using it needs to understand what the risks may be.

I use old stuff for many things, just not the critical ones.

 

[redreuben]

The main issue with old polyester is if it hasn't sealed properly in its storage container the styrene evaporates. If the viscosity is good catalyse at 1.5% spread it out in a paint tray and measure the gell time.