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Thread: Catalysts

  1. #1
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    Catalysts

    Hello - I make wood signs and use resin to fill in routed shapes. In the past I have used high street resins which were ok but I have just bought some of yours which I am hoping will be better.

    I bought the slow catalyst and the can comes with a standard pack. Not having any experience with these kinds, do you add normal catalyst to the resin AND the slow or is the slow a substitute for the normal one.

    Thanks.

    Also if you have any general tips on how to get very non-viscous resin and for it to set in a long cure that's what I am after - an overnight cure is fine. I bought a can of styrene solution in the hope that this is the right thing to add to make it less viscous.

  2. #2
    Super Moderator Alex's Avatar
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    You add only one type of catalyst. So slow is a substitute.

    You will probably find our resin much slower than 'high street' resin anyway, but you shouldn't aim for a setting time of the whole night, polyester resin must cure faster than that.

    Should you use slow catalyst at room temp at 1%, expect a useable time of 1 hour (ish) but the set solid time will be a few hours. I would consider this very slow indeed.

    You can add styrene to resin but remember that it will also dilute the other ingredients too so it will slow resin down even further. There is a thin line between a slow cure and not curing at all.

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    An hour or even half hour would be great but I was getting about 4 mins with commercial stuff which was way too fast and not enough time to pour it around all the grooves and channels and then brush it into crevices and remove bubbles. Often it would gel up and go hard in the pot whilst in the pour.

    I haven't checked how viscous it is yet but ill try up to 5% styrene and maybe 2% slow then. Sounds like I need to do some trials.

    I reckon I will have to get some fine pipettes too for the amounts of addition I will be using. I expect that most of your customers use a fair bit at a time.

    Thanks for the reply Alex !

  4. #4
    Super Moderator Alex's Avatar
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    Yup, the stuff you get from halfords etc is meant for small repairs and designed to cure really fast, our resins are for larger projects hence the speed difference. I'm sure you'll find the best combination with a few experiments, Good luck.

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    Hello Alex, I was wondering if you could add some more advice about catalysts. I have tried out the water clear casting resin with standard rate catalyst and mixed two small batches to test it. One was clear, the other I added pigment and a little styrene.

    I mixed up the two batches as 25g pots with 0.5ml of catalyst which if I am not being short of grey matter is 2%. I mixed for quite a while ensuring that I scraped the edges. I poured it into test panels and stood around for maybe an hour checking it but neither hardened. I took the clear mix pot and put a heat gun on it for a while and within a few mins it went to a gel and then hardened. So I left it overnight. Next day the clear appears to be firm but not hard and the white mix is still fluid.

    My workshop is cold with no heating left on overnight so I have put the fires on now and mixed a third batch being really careful about the ratios. Just clear with catalyst this time.

    So my questions are:

    * How close to tolerance does the 1% - 3% have to be ?

    * If I had to add styrene, then would it be better to add the catalyst to the styrene first and mix that up and then add it to the resin so it was more evenly distributed. I.e. could I have a small bottle of premixed 1:1 or 2:1 styrene / catalyst and then measure out 2ml of that instead of 0.5ml of catalyst alone ?

    * Is there a minimum temperature where these resins will not cure even if the mix was accurate and thorough ?

    * And do you think it will cure eventually or if I add heat now (after 24 hours or so) ?

  6. #6
    Super Moderator Alex's Avatar
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    Small mixes of such a pure resin can be problematic. There are a few issues to address.

    Styrene: Remember that this will dilute the resins active ingredients, in particular accelerator, which will retard the cure or too much styrene will halt the cure altogether. Combine this with pigment, that is also doing the same thing, and you can start running into problems where the resin is just overpowered with other additives.

    Temperature: Low temps are obviously going to slow things down, too cold and it can stop curing but chemical reaction heat (exotherm) helps the resin cure itself despite lowish temps BUT if the resin is spread thin then this will have less effect than if if were, say, a cube shape.

    Also crystal clear polyester resin is classed as inhibited surface resin. This manifests itself as a tacky film on the resin and is due to moisture reaction in the air. Very slow curing resin will have more tack than a resin that cures very quickly, as it will have more time to develop tack during the long cure.

    If i was to make a very small castings such as 50ml. I would pop it in an oven at 50c for 10 mins (not a hard and fast rule!) to induce a very fast cure and prevent issues from surface tack or low exotherm. This resin should cure (with no other additives) at between 1-3% no problem at room temp (surface tack excepted).

    I would expect you to struggle somewhat getting the pigmented test mix to cure properly in this case.

    Edit: Sorry if i have repeated any earlier advice!
    Last edited by Alex; 12-02-2015 at 14:51. Reason: I am an advice robot. Here is where i apologise for repeating myself

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    Thanks for your response and I welcome too much advice !!!

    So is it the case that with the crystal clear polyester resin that it would normally cure with a tacky surface or that getting a tacky surface is a risk from not having it set in a short time ? Once its tacky is there any fix for it ?

    I'm thinking of building a small temperature controlled oven as it seems that the temperature is a lot more important than first appears.

    What type of resin would you recommend for me. I have wooden signs with channels of lettering and designs routed in them at maybe 1-3mm deep. I can either paint the base wood and fill it with clear resin or colour some resin and drop it in and then sand it back to the wood surface level.

    I found the crystal clear resin to be about the right viscosity without styrene and its wonderfully clear so white goes real white not a pink shade. So I will probably drop the styrene and probably drop the slow catalyst since this normal one is being very slow anyways.

    Here is a link to a sample sign...
    Sign
    Last edited by Redrobes; 12-02-2015 at 17:12.

  8. #8
    Super Moderator Alex's Avatar
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    The signs look great!

    You could try some wax solution added at upto 2% to eliminate the tack but (there's always a but!) it will reduce the gloss of the resin. Although this could be polished back up to a gloss after curing with an abrasive polish like Farecla G3 or auto glym paint renovator.

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