Using a hot air gun with epoxies

[marwady]

I did a search and did not come up with much so pardon me if this has been posted before.

One of my favorite techniques for using epoxy is to heat it before applying with a heat gun or hair dryer.

It will quickly get much thinner and flows nicely into wood grain and joints. This works best with the longer time versions (30 and 45 min.) but you can also use it with the shorter cure.

I find that I can use much less glue and get the same or better strength and lighter weight.

Give it a try the next time you coat a baffle or want internal joints to flow into the nooks and crannies.

One note is that it will probably shorten the cure time, but not by much.

Best and Cheers!!

 

[blackbrandt]

Gee, thanks for telling me this before I cursed at my aeropoxy for half an hour...

 

[CarVac]

Gee, thanks for telling me this before I cursed at my aeropoxy for half an hour...

Which type of aeropoxy do you have? ES6209 structural needs no thinning to seep into wood grain, and it's easily spread into extremely thin layers. The laminating kind is... made for soaking into fiberglass, kevlar, and carbon fabric, not wood.

 

[troj]

Heating epoxy can indeed be handy, and if done for sustained periods of time, will shorten both working and cure times.

That said, be careful of the epoxies you do this with -- West Systems working and cure times can be made very short, without a lot of heat. AeroPoxy and Fibreglast are both much more tolerant of heat.

In addition, many epoxies have a maximum recommended temperature for when they're in liquid state.

-Kevin

 

[Pat_B]

I agree with Troj. It's rarely necessary to use heat with West Systems because it's darn thin to begin with. But the heat sure will speed up curing super fast. I also do very thin layups for FAI rockets and have to be careful about melting the mold release wax prior to the epoxy curing.

 

[CCotner]

Aeropoxy loves heat. It cures harder, stronger, stiffer, and faster. It gives off heat as it cures, so it's easy to (with a low-temperature oven) really warm up the curing laminate and get the best (better than spec) results.

But why on earth were you cursing your aeropoxy?

EDIT: It just dawned on me how freaking often I extol the virtues of Aeropoxy here on TRF. I want to fully disclaim that I am not a spokesperson of Aeropoxy, PTM&W, or any of their vendors. I just freaking love their products. =p

 

[jimzcatz]

I work out in a cold shop. Even though I have a propane heater, the epoxy is like molasses. I am talking the hobby epoxies. I just nuke it in the microwave(no longer used for food) before I mix. Makes it flow much easier out of the bottles. All it takes is about 10 seconds.

 

[GregGleason]

FYI:

Most US consumer blow/hair dryers are limited to about 140 F (60 C) by the CPSC. Heat guns can go from 500 F to 1100 F (260 C to 593 C).

So for epoxy processing, blow/hair dryers are likely the most suited tool to heating epoxies.

Greg

 

[cavecentral]

I've tried the heat gun to speed up a nose cone layup. If you use the pink foam insulation, it melts. This makes your mold become mishapen and the nose cone look funny.

I have stuck a cone in the oven on a cookie sheet at 170 degrees (lowest it goes with the door open). Not sure I recommend it either, but it did speed the cure.

 

[G_T]

Higher temperature will speed the cure, sure. BUT if the temperature is too high, or too high too soon, the result is brittle. That might not be what you want. Please take a look at the tech sheets on the epoxy you are using before using much heat.

If you find that the epoxy you are using is too thick, use as thinner one for the job.

Gerald

 

[marwady]

Lots of great ideas and experience from all the members here!!

I will add that I only use enough heat to get the viscosity I desire.

On the hobby grade epoxies I use, it does not take much more than 10 - 15 seconds to get it where I want it with the gun set to low.

I hold my gun about 15 - 20 inches away from the mixture to be heated.

I usually mix first before I heat however, my garage, though heated, gets pretty cold in winter.

In that case, I will hit each bottle for about 30 seconds, rotating for even heat.

As always YMMV.

 

[blackbrandt]

Which type of aeropoxy do you have? ES6209 structural needs no thinning to seep into wood grain, and it's easily spread into extremely thin layers. The laminating kind is... made for soaking into fiberglass, kevlar, and carbon fabric, not wood.

structural from GLR... Pint kit. I was trying to suck it through a syringe yesterday and it refused. True, it was only 40* in the shop...

But why on earth were you cursing your aeropoxy?

Because thick epoxy+syringe equals not fun, Hard cleanup, difficult to drip into a nose cone, etc...

 

[CarVac]

structural from GLR... Pint kit. I was trying to suck it through a syringe yesterday and it refused. True, it was only 40* in the shop...


Because thick epoxy+syringe equals not fun, Hard cleanup, difficult to drip into a nose cone, etc...

Step 1: Pull the plunger out of the syringe.
Step 2: Mix up some Aeropoxy.
Step 3: Take a popsicle stick, gather a huge glob on the end, and insert the epoxy into the open end of the syringe.
Step 4: Insert the plunger, point the syringe up, and squeeze out the air.
Step 5: ???
Step 6: Profit.

By the way, it's rather fun to experiment and see how big a glob of ES6209 you can keep stuck on a popsicle stick: I can hold a ball of around a centimeter diameter by tilting the stick back and forth while hanging the glob beneath it.

 

[blackbrandt]

How big of a syringe should I use? I have been using a small 1/8 inch diameter syringe, should I use a bigger one?

 

[troj]

How big of a syringe should I use? I have been using a small 1/8 inch diameter syringe, should I use a bigger one?

That's probably a 10cc syringe. Get some 50 - 60 cc syringes (they're about 1/4" dia). A couple years ago, I bought a box of catheter tip syringes, which work very well for epoxy.

-Kevin

 

[troj]

If you're working with West Systems epoxy, here's some of their info on heating epoxy.

CAUTION! Heating epoxy that has not gelled will lower its viscosity, allowing the epoxy to run or sag more easily on vertical surfaces. In addition, heating epoxy applied to a porous substrate (softwood or low-density core material) may cause the substrate to "out-gas" and form bubbles in the epoxy coating. To avoid out-gassing, wait until the epoxy coating has gelled before warming it. Never heat mixed epoxy in a liquid state over 120°F (49°C).

I added the underline to the bit regarding their epoxy, in liquid state.

Other epoxies are different; AeroPoxy and Fibreglast can both be heated more, in their liquid state.

Someone said earlier to make sure you understand the characteristics of the epoxy you're working with. When using heat, this is very true.

-Kevin

 

[CarVac]

Aeropoxy datasheets pretty much clearly state that they can be cured at 140 F, and they cure in a hurry.

 

[G_T]

I don't recommend heating FiberGlast System 2000 all that much to be honest. It strongly exotherms and it is easy to smoke it or damage it. It may not be obvious that one has done so. But if a little bit too much heat is applied, then the resultant epoxy when cured is not as strong or as stiff. I've hit this issue by applying heat so I'm speaking from experience here. The areas which had a little too much heat would deform under sustained pressure and the areas which did not have too much heat would not deform.

Gerald

 

[troj]

I don't recommend heating FiberGlast System 2000 all that much to be honest. It strongly exotherms and it is easy to smoke it or damage it. It may not be obvious that one has done so. But if a little bit too much heat is applied, then the resultant epoxy when cured is not as strong or as stiff. I've hit this issue by applying heat so I'm speaking from experience here. The areas which had a little too much heat would deform under sustained pressure and the areas which did not have too much heat would not deform.

How warm did you get it? As I recall, for maximum strength, you're supposed to heat cure it somewhere around 180 - 200 degrees.

-Kevin

 

[CarVac]

How warm did you get it? As I recall, for maximum strength, you're supposed to heat cure it somewhere around 180 - 200 degrees.

-Kevin

Usually a cure at that temperature is reserved for either prepreg resin or a post-cure, not the initial cure of a room-temperature curing resin.

 

[JoeG]

As one who has used pretty much every adhesive and paint known to man in the auto body repair business please be careful of the fumes when you heat epoxy. Or any time for that matter but they seem to be more intense when heated. Most resins seem to have little lasting effect on general health but some of the hardeners can be pretty mean and cause permanent respiratory problems. The term "Use only in a well ventilated area." comes to mind.

Again, be careful.