Hi guys,
I am using Adtech 820 epoxy (with carbon and glass) and demolding time is 24 hours, I am making flat panels on a big piece of glass (roughly 24" by 60") now is there anyway to make the demolding time shorter? I do have heating blanket and I have heard heating lamps work too, but has anyone have any advice or tip on this? how much temp? when to start heating up and etc
Thanks
Typically, I don’t like to start adding significant heat until the resin has set. I will often initiate the cure at around 85F to 90F. Once the resin is hard to the touch (resin smear on curing card) I will ramp (15 degrees per hour) the temps up to 150*F. If you add too much heat too soon you can end up with less cross-linking due to a poorly established molecular lattice. I’m used to making critical structural parts so I want to maximize my potential of my resin. You can clearly add more heat sooner but this typically will reduce the potential of the resin. It’s quite debatable to how much difference it makes…I lean toward the safe side.
I still cure for at least 14 hours or more. Early demolding is the leading cause for fabric pattern print-thru.
You might consider making a foam box that can be lowered from the ceiling or simply placed over the layup. In this scenario you could put the glass & layup on top of a piece of foam. Many people for low heat applications will just use light bulbs inside the box. You can screw and unscrew the bulbs to vary the heat. A simple 120 volt fan like this one can be be suspended from the roof of the box to circulate the air for even heating. An IR thermometer can work well to get instant readings on the temp of the layup.
Adding heat before the resin is cured is no problem. Normal the epoxi will crosslink better if you add heat.
But if you cure at a high temp you will have inner tensions in the laminate. But if you produce a exhaust heat shjeld it can help to cure hot because then there are less tensions in the laminate at working temp.
Of use a faster hardener. (or both).
You could also add heat tracing to the mould, albeit more expensive.
Keep in mind the mould should be capable of the heat as well.
Thank you for response … Another somewhat related Issue I just had yesterday. For the first time I infused a panel at night and it was around 55F and after demanding I had pinholes through out the whole panel! I have been infusing the same way with no problem before and I am sure there was no leak and I degassed the resin. So does infusing at lower temps increase the risk of getting pinholes?
Yes, the viscosity went up, so the saturation and impregnation of your fiber went slower.
Always keep a good temperature!
If the temp is lowewr the viscosity of the resin gets higher and the resin will not soak thru the fabric as easily, in effect it will more pass over the fabric than soak down and pass over at the same time. therefore there will be dry areas of fabric (not dry enough to cause dry spots) that in effect mean that there is not full film of resin on the surface.(and hence pin holes)
I am using Adtech 820 resin with 823 hardener. The cup life is around 45 minutes and I can demoed after 12 hours. I just pulled a part after about 14 hours and it came out perfect.
i use the same hardener dpaine, I am gonna see if 12 hrs is enough next time i infuse something. thanks
You can use cheap electric blankets to heat the mould before and after infusion. They heat slow and work well.
Just wrap your part with the blanket and controll your temperature. There will be a temperture peak and than you can switch off your blanket.
This has worked extremely well for me as well. I put the heating blanket over the mold and then wrapped the whole thing in garbage bags to reduce convective heat loss.
An extremely ghetto solution, as it’s sometimes described in California, but it reduced my cure times from 24 hours to 8 which I was very pleased with.
usually every 10 degrees halves the time. I can demould parts after a 1,5 hour cure, wich usually takes 12h. I cure at 30 degrees celcius for half an hour to let te epoxy gel, then raise to 60 for an hour, with increased vacuum (80%). Be carefull with temperature and pressure, you can suck out too much resin 
Agreed heat blankets and breather works great