Cold temps, will my part cure?

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#1

Hi all, I have laid 3 8 oz glass cloth layers with poly. i catalyzed at 1.5% The garage this part is in cycles from 68 F to 35F from when i am working in there and at night. The longest the garage has been 68 is maybe 4 hours. It has been maybe 3 days since this lay-up and i am still in gel stage. I have left a quarts heater in front of one section all day today and will check when i get back ( maybe 8 hours exposure). I am concerned that all the MEKP may evaporate by the time my part cures and will leave my part in eternal gel. What should i do at this point

the body in front of the quarts heater gets quite warm, maybe 100F

Thanks

#2

The chemicial reaction from the MEKP will be gone but the heat from the lights will finish it off!

#3

thanks for the reply, so have i learned something here? MEKP is a catalyst which only helps the poly base reach its activation energy and it is possible for poly to cross link without the specific MEKP as long as the activation energy requirement is met “heat”.

And when i say cross link, i mean just change state in whatever specific way it does.

So if this is the case, then i will just move that quarts heater around the entire thing.

THANKS

#4

The MEKP reacts to the Cobalt in the PER to make a chemicial heat reaction…

There’s even an UV curing PER where to lay it up and place it outside or under UV lights too!

#5

Some times I have the same problem. So, I fix one small room from metal sheets and I put one air heater on it. Now I have over 37Celsium and the progress are fast.:smiley: The air heater is without fun.

#6

I built a hot box for my part and got the top up to 130F and the lowest parts to about 110 F. I let the part heat for just over 3 hours. When i killed the heaters some areas of the part were still soft and left a thumb print but this morning after a nice heat taper down to ambient it seems my part has cured.

here is my part in its hot box:

#7

Would temperature differentials of 20* F be enough to cause curing issues, since different parts of the composite are reaching green cure and final cure stages, and thusly, shrinking, at different rates and times?

#8

Yes or not enough proper mixing the MEKP & PER too.

Also the laminate thickness has effects too: Thin less reaction and heat , thick extrotherms with excess heat / reaction!

I always show the class by mixing up a hot batch 10% mekp to PER and do a thin / little test panel, it gets to maybe 80 / 90 degrees and the excess in the cup goes over 350+ degrees until it is smoking and smelling up the place! Then I show them how to use a glove, pick up the hot smoking cup, walk with it behind their back (in front of you and you are getting the bad fumes…) to the back gate where there was 2 water buckets to throw it in…

#9

I melted a plastic mix cup once with left over fast cure epoxy.

#10

what are building there unimog? looks like some kind of car project…

#11

Seems to be no issue with the part, it is hard as rock and i couldn’t be happier. Dimensional stability is not a big concern of mine since i shaped the entire plug by hand and I am sure its not perfect. This is a back section to a FF (formula ford) that previously had no back. I had an issue with the back tail flat part where it was just too flimsy. i thought this would be the case since it’s just flat with not much inertia (stiffness) but i didn’t think it would be this flimsy. Solution: i made a jig to reference the tail flat with the rest of the body and on the tail underside i am in the process of honeycombing it. It’s working perfectly so far. I will have to post some pics to explain better.

#12

That’s a Formula Ford. An 85 Van Dieman or possibly a Reynard. Pretty standard really in the Formula Ford world of racing cars.

#13

crossle 65

#14

I finally got a 65k btu diesel,kerosine type heater. turbine type. whats the best way to get the most use of this? seems as if the front of the Shop is heated, but towards the back its super cold. should i get the same type of heater but that goes in the ceiling?

#15

Anyone out there that is looking for heaters for your shops (I won’t tell you what So. Ca. temps have been…) try the thrift shops and look for quartz tubed room heaters. They heat the objects in the room and some of the air too plus no flame!

#16

if your fuel type heater is to be used indoors you should use kerosene as it is specific for this app. Kerosene has far less sulfur in it than diesel so it is better for you. Werksberg is correct though about quarts heaters, they provide radiant heat which warms up surfaces much better than just convection type heaters. Kerosene is roughly 270$/gal here in MA and i haven’t done the comparison verses using only quarts heaters on a cost basis. do the obvious steps as in sealing any drafts and insulate , the plastic window covers work well for leaky windows. Based on the part requirements i would recommend quarts heaters they are usually in 750 and 1500 W.

#17

Ok. Assuming your figure of 65K BTU is BTU/hour, then this is equal to 19K watt which is equal to (12.6) 1500 watt quarts heaters. thats right almost 13 quarts heaters can replace the heat output of you fuel heater on max output. Again there is something totally different between heating the room and heating the part/surfaces

#18

The one big advantage to an electric-type heater as opposed to a combustion setup is venting!!

While any shop should be ventilated, as soon as you’re burning fossil fuels to create heat, the venting requirements for the shop should increase…so while you’re venting out the carbon monoxides and dioxides, you’re also losing vast amounts of heat.

In terms of efficiency, my guess would be electric, by far.

#19

If only a small area if a part is not properly cured, what can of defects would we see?

#20

Weak, rubber and sticky to the hands. (I’m now doing my best Rolling Stones imitation of “STICKY FINGERS”!)

Just place in the sun during a sunny day or inside a glass window or under quartz shop light and the heat will help finish it off.