Fiberglass cure question

[gm280]

I have to concur with SD above. You need to get your supplies from another supplier. When you say dries, are you allowing it enough time to cure? How long after applying the polyester are you allowing? If that time is merely an hour or so, you need to wait longer... JMHO

 

[Woodonglass]

Did you use CSM?

Try this Mix a small amount of resin with the hardener and put it on some wax paper about an 1/8" thick. Let it set for and hour. NO CSM! After and hour it should be cured, very hard, and brittle enough to break with your fingers. If not...then the resin and or hardener is BAD!!! Poly Resin is very hard and brittle without CSM and Fabric.

 

[Rickam]

I'm coming around to the conclusion, per several of your responses and also a local boat builder I consulted today, that the resin is bad. The seller has offered to replace it and I'll try that first, then buy elsewhere if no improvement. Fortunately this is a personal project, not my livelihood. The local guy also recommended that I coat the raw wood with epoxy rather than polyester due to better bonding. Does that sound right? Thanks.

Rick A

 

[zool]

I'm coming around to the conclusion, per several of your responses and also a local boat builder I consulted today, that the resin is bad. The seller has offered to replace it and I'll try that first, then buy elsewhere if no improvement. Fortunately this is a personal project, not my livelihood. The local guy also recommended that I coat the raw wood with epoxy rather than polyester due to better bonding. Does that sound right? Thanks.

Rick A

No it doesnt sound right, poly has a tough time adhering to epoxy if any amine blush remains...coat with poly if tabbing with poly.

 

[Scott Danforth]

You either go all epoxy and paint

Or

All poly and you can gel, paint, etc

You dont mix

 

[tpenfield]

That is why I asked if the plywood was previously coated with epoxy. It will prevent the poly from curing.

 

[Rickam]

Thank you all again for all your shared wisdom. After over twenty years of finding answers to my questions online I still marvel at how a good share of the world's collective knowledge is available right at my fingertips!

Rick A

 

[tpenfield]

Let us know how things proceed with a new batch of resin, etc.

 

[Redtruck12]

So what is considered an expectant life for poly resin?
i have 2/3 of a 5gallon pail remaining from fall 2018.
will it likely be okay this spring???

 

[Woodonglass]

So what is considered an expectant life for poly resin?
i have 2/3 of a 5gallon pail remaining from fall 2018.
will it likely be okay this spring???

A lot depends on how it was stored. If the lid was on tight, and it was stored in a cool dry place (both resin and Catalyst) then it can last up to 6 - 12 months. Best thing to do is mix a small batch and see how it does.
To be safe it's always best to use the resin and hardener within 3 months of it's purchase.

 

[gm280]

The easiest way to determine if it is your supplies, is to see if the brush, roller, and anything remaining in the container ever cured. If not, bingo, you have bad supplies. That rules out the wood and everything else. JMHO

 

[Rickam]

Hello again,

OP here. I explained my problem to my supplier and he sent me replacement resin; no help. I bought hardener from a local store; no help. Tried some fresh hardener from a local boat builder; no help. With each attempt I mix a small amount and coat a scrap of cloth, which dries non-tacky but soft and flexible. I noticed the new resin the supplier sent me was quite a bit darker in color than the original- don't know if that indicates anything. Next desperation move will be to buy some resin and hardener locally and try it, I guess. I'm preplexed!

Rick A

 

[tpenfield]

The resin does not dry, it cures . . . meaning it turns into plastic.
.
A single scrap of fiberglass cloth may be flexible after the resin cures, merely due to how thin the piece is.
.
Are you able to get a small sample (1-2 ounces) of the resin to cure solid if left in a mixing cup?
.
Are you able to get a small sample of the resin to cure on and adhere to the plywood piece that you were trying to encapsulate?

 

[alldodge]

Several suppliers and all not working, tells me its not being mixed correctly or temps not right

 

[gm280]

Are you using mixing cups to mix your resins? I ask because with measured mixing cups, you know exactly what amounts you are mixing up each time until you get use to the amounts needed. Don't try to use both oz's and cc's or ml's measurements with the same mix. Use cc or ml measurements to keep things easy. If you pour 200 cc (or ml) of resin, then you need 2 - 2.5 cc's of MEKP.

If all else fails, buy some from US Composites in Florida, and be a happy camper...I mean boater!

 

[froggy1150]

I make mixers for my drill. Take a coat hanger fold in half then twist. On the end make it t shaped. I also bend the ends of the t so it don't dig into cup. My resin is amber. And when I mix it turns purplish. From that point .... 1.5-2 min. Not too aggressive so you don't get air bubbles in mix but at this point just try for cure

 

[gm280]

I have to say, my very first polyester resin mix took DAYS to cure. And I can tell you I mixed so precise that it was spot on. And that worried me to the point that I asked questions on these forums as well. But the second mix cured perfectly. I don't know why, but since that time, I know I have mixed maybe a hundred mixes and not one failed. I have mix 23 gallons of polyester now, and I stopped measuring any MEKP anymore, because I can see if I use the proper amount from experiences. Not one failure.

But I will say, I exclusively use US Composites polyester resins and MEKP hardeners and associated fiberglass materials. They ship very quickly and their resins are always fresh and ready to use. No old sitting-on-the-shelf products with them since they do such huge volumes of supplies daily. JMHO

 

[tpenfield]

Throughout this thread the information that 'we' have received from the OP has been a bit vague at times, often raising more questions than answers.

Rickam we are all trying to help, but it seems like we still don't know specifically enough about what you are doing/seeing.

 

[Ciera2450]

Agreed.. fiberglass will more likely to cure faster/quicker/more often than you want it to. Not the other way around.

Has anyone asked yet.... are you using MEK instead of MEKP by chance? That might cause these issues.