How much mekp?

[Dennischaves]

I always mixed my polyester resin with 1% MEK (16oz resin to 5cc mek)
Can i mix it at 3/4% mek ?
About 4cc to 16oz resin or will it be to little harder
I just want a little longer working time

 

[Ned L]

I certainly am no Polyester resin expert but thinning with MEK is a new one for me.

 

[Dennischaves]

Thinning with mek???
Thats not what i was asking

 

[jbcurt00]

I certainly am no Polyester resin expert but thinning with MEK is a new one for me.

I suspect he meant MEKP, the catalyst, not MEK, the industrial 'thinner'....

Do smaller layups, unless you're somewhere its already above 80F every day, and work in the shade.

1% is a pretty low catalyst rate, bottom of the allow range for resin I've seen. You're actually slight higher then 1%... For 1% w 16oz resin (473ml) you'd use 4.73ml.

17oz resin is 502ml, so 5ml MEKP to 17oz of resin would be extremely close to 1% and at a lower ratio then you're using now.

Why measure resin in Oz and MEKP in mL? Much easier to use ml for both....

Keep the resin inside a cool area until you mix it. If the resin is 65F when you mix it, it will slow the reaction, if only a little..

 

[Dennischaves]

Ok thankyou thats what i wanted to know
And yes MEKP my error

 

[tpenfield]

If I were me, I would not go below the 1% ratio of MEKP, because it may not cure properly. Cool the resin down for a longer working time. Once you are done laying things up, you can hit the areas with a heat gun to accelerate the cure, if needed.

 

[Ned L]

Ahhh, ... ok.

A larger diameter, shallower container will also extend the working life a bit (it won't heat itself up exothermicly so much)

 

[gm280]

1% is about it. You can try 1/2% but I would do that as a very small batch to try first. My very first poly mix, I used the instructions that came with the polyester resin. I was using U S Composite's 435 Polyester resin and mixed it per their instructions. It took three days to harden/cure. I honestly didn't think it would ever. So just try very small batches to see. All that could happen is it doesn't set and cure. But on something that you don't care about, would let you know. JMHO

 

[Woodonglass]

Several years ago one of or Expert Members OOPS, posted a some great info on resin mixing. In it he stated the .75% was the minimum you should go with and you really need to ensure proper mixing. With High temps 95?+ would be when you'd need to do this. As mentioned using larger containers and working in the shade is another method to extend work time.

 

[tpenfield]

FWIW - In cooler weather (60's F) I go 1.5% MEKP with poly and up to 2% with Vinyl Ester resin. If I need more working time, I just cool the resin overnight, before activating it.

 

[Dennischaves]

Thanks everyone for your help
I will stick to 1% mekp