Questions on mold temperature maximum and curing temperature maximum


Questions on mold temperature maximum and curing temperature maximum
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ahender
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Tomorrow I will finally infuse the 12' canoe I have been working on for years. I'm going to preheat the mold and I want to elevate the temperature some during the curing process.
What is the ideal temperature I should aim for regarding the mold? The resin I am using has a cps of 600 so I think it needs to thin some once it hits the mold.
I also want to elevate the temperature once the infusion has completed. Is there a limit as to what this temperature can be?
Thanks again for offering such a great resource for those with limited knowledge in this area.
Alan


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Chris Rogers
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You want to get the right balance between resin viscosity and gel time for the infusion layout you're using.  So, not knowing anything about your tooling, materials or resin... I'd suggest a few things:

1 - Make sure your resin and mold are the same (elevated) temperature - so heat the resin too.  Just let the pails hang out in the hot room with the mold over night.  If the 600cps is at "room temperature" the viscosity will be much more usable at 90F / 32C or even higher if you can do it - usually with epoxy uncomfortably hot is ideal.  What is the resin system you're using?  Some epoxy tooling systems are that viscosity and need to be infused hot (like 40C or more), but most general purpose infusion resins should be lower viscosity...

2 - Don't change / raise the temperature until the resin has all gelled - then you can ramp it up a bit and do a postcure.  If you heat it before it gels, you risk changing the vapor pressure situation and potentially having bubbles form or other issues.  Once it has gelled hard, go ahead and ramp it up slowly.

3 - I'd suggest leaving your vacuum on and (ideally) dialing it back to 20inHg or so after the part is filled.  Leave the vacuum on through the full cure cycle - including the postcure.  If you don't have the option of very high vacuum, it is sometimes ok to do the whole shoot at 25inHg or so and just throttle the fill so you don't have trapped air problems.  If this is a very light laminate (canoe) then it shouldn't be an issue.  Are you using core?

4 - Make sure you have good resin breaks so you don't have over-bleed issues as you wait for the resin to gel...

Good luck!  Please post some pictures of the canoe if you can.




ahender
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Chris Rogers - 10/15/2020 3:30:09 AM
You want to get the right balance between resin viscosity and gel time for the infusion layout you're using.  So, not knowing anything about your tooling, materials or resin... I'd suggest a few things:

1 - Make sure your resin and mold are the same (elevated) temperature - so heat the resin too.  Just let the pails hang out in the hot room with the mold over night.  If the 600cps is at "room temperature" the viscosity will be much more usable at 90F / 32C or even higher if you can do it - usually with epoxy uncomfortably hot is ideal.  What is the resin system you're using?  Some epoxy tooling systems are that viscosity and need to be infused hot (like 40C or more), but most general purpose infusion resins should be lower viscosity...

2 - Don't change / raise the temperature until the resin has all gelled - then you can ramp it up a bit and do a postcure.  If you heat it before it gels, you risk changing the vapor pressure situation and potentially having bubbles form or other issues.  Once it has gelled hard, go ahead and ramp it up slowly.

3 - I'd suggest leaving your vacuum on and (ideally) dialing it back to 20inHg or so after the part is filled.  Leave the vacuum on through the full cure cycle - including the postcure.  If you don't have the option of very high vacuum, it is sometimes ok to do the whole shoot at 25inHg or so and just throttle the fill so you don't have trapped air problems.  If this is a very light laminate (canoe) then it shouldn't be an issue.  Are you using core?

4 - Make sure you have good resin breaks so you don't have over-bleed issues as you wait for the resin to gel...

Good luck!  Please post some pictures of the canoe if you can.

Thank you for the detailed response Roger. The resin system used for the mold is epoxy sanded to 1500 grit. Six applications of wax have been applied. The epoxy I am using is from US Composites. The fabric is 9oz/yard s2-glass. The peel ply, bagging film, and mesh are from Easy Composites. No core for this layup. One layer of glass all over, then an extra layer on bottom, bow, and stern. After cure, I will add a core, then separately another layer of glass. 
The canoe is designed to be an ultralight, hence the use of only one primary layer of glass on outer and inner layers.

I do plan on dialing back the pressure after the infusion. The mesh will stop about 3 inches from the end of the fabric. There will be about 6 inches of just peel ply between the glass and vacuum line.

So to confirm, you are stating both my resin and mold can be heated to 90 degrees F for the infusion? Then continue cure as the same temperature until the part has gelled?

One question. Why does there need to be a vacuum after the part has gelled?

Alan




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ahender - 5 Years Ago
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             Thank you Warren.
ahender - 5 Years Ago

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