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Ted
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Quick Update . . . I wanted to close things out on my extended swim platform project, which is now done. Here are a couple of pictures of the final result mounted on the boat.   The TBC inhibitor worked well to allow a good 75 minutes of open time for the mold infusion. I did use MCP catalyst on the actual part infusion rather than the TBC. I ended up infusing the outer layers of the part, but then switched to hand layup for the core and inner layup lamination. The resulting part (i.e. platform) was surprisingly light (100 lbs w/out hardware) and quite rigid and strong, which was a goal of mine so as not to add too much weight to the stern of the boat. I'll be testing it out for real over the next few weeks 
It was certainly a learning process for me, but I am pleased with the results. If I had to do it again, I could probably do it in half the time and half the cost. So, there is the price of learning, I guess. 
Regards, tpenfield
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oekmont
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Nice to see that you got your desired result in the end. Inhibitor is a very useful tool when working with polyester, and most people don't know of it's existence.
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Ted
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Update . . . I wanted to close the loop on my original question about resin fill times. I did the infusion today and used the following techniques to get a reasonable result. TBC @ 300 ppm MEKP @ about 2% . . . maybe a touch under Temp was on the colder side . . . 60˚ F I elevated the bucket, so the resin flow had gravity assist, and made sure to have an ample runner system.  The resin filled fairly well and the working time was 75+ minutes. Here is a picture at about 30 minutes into the infusion  I do like the TBC inhibitor vs. the MCP catalyst, particularly for colder temperature infusion. Once the resin starts to kick there is a decent amount of exotherm. Thanks to everyone for your input and comments.
Regards, tpenfield
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Ted
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+xwhy polyester resin and not epoxy? because of the price? epoxy would solve your problems with the cure when you take a slow infusion resin. But if you choose polyester resin you should be ok with using a small amount of MEKP. Keep in mind that the polyester resin will boil under vacuum. 0,6 bar should be the vacuum you are aiming for. About your pressure + vacuum, I think you'll have some problems. if you have -1 Bar vacuum and add +1 (or more) of pressure in your pot, you'll end up with 0 bar of pressure in your bag. At least if I understood well what you are planning to do. Poly tastes better 
I figured with a delayed gel time that I can get from either MCP or TBC, then I don't need to pressurize the resin feed. A bit of gravity would probably do the trick.
I'll keep an eye on the vacuum pressure. Within the mold, the resin should 'feel' the pressure from the outside air pressing on the vacuum bag as it saturates the fiberglass. I have done a couple of test infusions and no 'boiling/degassing' of resin. I was pulling about 25 in Hg (0.85 bar) of vacuum. I could see that a rigid mold might have more of a boiling problem.
I'm still working out a few bagging seal issues on my swim platform plug, but hopefully will get the 'big infusion' done within the next 2 weeks.
Regards, tpenfield
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Matthieu Libeert
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why polyester resin and not epoxy? because of the price? epoxy would solve your problems with the cure when you take a slow infusion resin. But if you choose polyester resin you should be ok with using a small amount of MEKP. Keep in mind that the polyester resin will boil under vacuum. 0,6 bar should be the vacuum you are aiming for. About your pressure + vacuum, I think you'll have some problems. if you have -1 Bar vacuum and add +1 (or more) of pressure in your pot, you'll end up with 0 bar of pressure in your bag. At least if I understood well what you are planning to do.
Matthieu Libeert
Founder MAT2 Composites X Sports
website: www.mat2composites.com  
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Ted
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 Just to follow up on my quest for a delayed gel time. I ran some tests of the various catalysts and inhibitor that you see above. Each sample is 0.75 fl. oz. (22 ml). The TBC is mixed into the resin at about 300 ppm. The MEKP and MCP catalysts were at 2% ratio to poly resin. The resin started out fairly cold (57˚ F, 14˚ C ). The 'open time' (liquid before gel) and maximum exotherm temp observed with an IR gun is noted above each sample. My preference is the MEKP w/ TBC, because it had a long open time, similar to MCP, but then really kicked into gear and cured fairly quickly, whereas the MCP took about 12 hours to cure to a similar hardness. I'm sure more temperature will help move things along faster, but all things being equal, I like the TBC as an inhibitor.
Regards, tpenfield
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Ted
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+xI ran a test and, like promised, 0,2% doubles and 0,5% quadrupled the pot life. But except for ec's pattern coat I never needed double pot life. I once had an uncomfortable fast laminating resin wich I slowed down with 0,1%. And for everything else, I used even less, if I got the feeling it could be tight on time. Polyester resins (and mekp) are so different in their reactivity and the pot life from the data sheets aren't always good. Testing is the key. I never do regular infusion with polyester, only vari, hand layup and RTM like processes, so I never used higher concentrations of the inhibitor. Why bother with acetone, if you could mix it straight into the resin? I have tracked down a supply of the crystal (flake) form of TBC. I had to order it from a retail supplier that acts as a middle-man between the commercial supplier and the end customer. It seems that the product you mentioned. . . Pergaslow BK-10 is not readily available in the USA. I did contact the USA division of Pergan (Pergan Marshall) but have not gotten word back. In the mean time, it looks like I will have a life time supply of resin inhibitor, once I mix it at a 10% solution (by weight) with either styrene monomer or actetone. I'm thinking styrene would be best. The smallest amount of TBC that I could order was 250 grams. I think I'll use not even 10 grams of it. However, after days of searching and contacting various companies, i'd just be happy to have some in hand. Along the way, I've also been steered towards a 'slow' catalyst . . . Norax MCP which gives about twice the gel time as MEKP. I'll have both to try and see which of the two works better for my situation.
Regards, tpenfield
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oekmont
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I ran a test and, like promised, 0,2% doubles and 0,5% quadrupled the pot life. But except for ec's pattern coat I never needed double pot life. I once had an uncomfortable fast laminating resin wich I slowed down with 0,1%. And for everything else, I used even less, if I got the feeling it could be tight on time. Polyester resins (and mekp) are so different in their reactivity and the pot life from the data sheets aren't always good. Testing is the key.
I never do regular infusion with polyester, only vari, hand layup and RTM like processes, so I never used higher concentrations of the inhibitor.
Why bother with acetone, if you could mix it straight into the resin?
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Ted
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+xThank you. That is very helpful. I'll see if I can get some from a USA based supplier @oekmont - It seems like I can only find TBC in the crystal (soild) form in the USA. Nothing that I could find in the liquid form. I believe the BK-10 is a 10% TBC solution. Do you recall how much of the BK-10 you have used to inhibit the resin cure times? It seems like inhibitors are used at a 100 - 300 ppm range to extend the gel times by 2-3 times their normal. I have styrene monomer and acetone, so I could possibly make a 10% solution from the crystals. Regards, tpenfield
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Ted
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Thank you. That is very helpful. I'll see if I can get some from a USA based supplier
Regards, tpenfield
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