Quick or slow set epoxy

For firewalls I use a combo of 5 and 30 minute epoxy. I put dabs of 5 on the corners and 30 for the rest. It keep the firewall tight while the 30 does it's thing.

I use 30 min. for all my epoxy needs.

For fuel proofing firewalls or tank areas, I need the extra work time. Generally, the joints where I use epoxy have at least one side being either plywood or hardwood and I think the slow set allows the epoxy to penetrate better. It also seems to be less brittle than the fast setting type.

30 minute expoxy is my preference for general work where parts alignment require some time for adjustments.

For fuel-proofing engine compartments, etc. I use Pacer finishing resin but only because I have lots on hand from another project where it did NOT work out well leaving a smooth glass-like finish.

Ron: re: 5 minute

So who's in a hurry? Certainly not me!

Relax and don't be so "up tight".

Thanks guys,

I think I have a better idea as to what each type of epoxy is used for now. I originally thought maybe it was a strength thing, but I see now it speeds up or slows down the workability of the product.

I ain't uptight Dave! I build a lot and usually I am in a time crunch so now I feel safe in using the quick set when I need it.

Ron

I reserve 5 min epoxy for field repairs.

George

Epoxy is finicky stuff. You need a quick set for when it is cold outside and working in the cold, and vice versa. Cold temps really mess with the chemical reaction of epoxy. I have since switched over to West Systems Epoxy.

Clipped from Jamestown distributors and is a interesting read for the most part. Since it is getting on to winter, I thought it would be appropriate and because some of us don't live in those warmer environments year round.
--------------------------------------------------------------------------------------------------------------------------

We know that most epoxies perform well or, at least reach a higher percentage of their potential physical properties, at temperatures of 60F and above. Some epoxy systems or resin/hardener combinations are formulated to cure in temperatures as low as 35F. However, simply using a cold weather epoxy system at this temperature does not guarantee dependable bonds. A number of other factors can significantly affect your epoxy's bonding ability in cold weather.
Epoxies can be formulated to cure under a wide range of conditions. However, each epoxy system or resin/hardener combination must be used within specific limits of application temperature, humidity, joint fit, surface preparation and cure time. They rely on a complex chemical reaction to achieve their strength and longevity, and disregarding their limitations can drastically affect the outcome of the chemical reaction and compromise the performance of epoxy bonds.

Epoxy can be used at cold temperatures, but must be handled and applied with techniques adapted to cold temperatures. This paper will discuss how epoxies work, why they perform differently under cold conditions, and what steps you can take to assure dependable bonds in cold weather. Chemical Characteristics
Mixing an epoxy resin and hardener together starts a chemical reaction which produces heat. This is called an exothermic reaction. The surrounding temperature affects the rate of the reaction and the degree of cure. Warmer temperatures accelerate the reaction, while cooler temperatures retard the reaction and reduce the crosslinking activity of the epoxy molecules. More time is now required to achieve the same degree of cure, or crosslinking, as occurs in a shorter period at higher temperatures. If the temperature is too low, the epoxy may eventually harden, but may not reach a complete cure or achieve its designed physical properties. Although the partially cured epoxy may have enough strength to hold the structure together, it could fail prematurely.
Epoxy joints in various structures are subject to different types of load during their working life. Many of the joints in a boat for example may be subject to millions of small repeated (fatigue) loads. Others must resist slow stretching and deforming under steady loads (creep-rupture).
One of the dangers in using epoxy in cold weather, is that epoxy that has not cured completely will be more flexible. Testing clearly demonstrates that increased flexibility seriously reduces an adhesive's ability to resist fatigue and creep-rupture. Information about fatigue, fatigue testing, and the how flexibility affects the fatigue life of epoxy, can be found in FATIGUE ASPECTS OF EPOXY AND EPOXY/WOOD COMPOSITE MATERIALS 002-545, published by Gougeon Brothers. The notched beam test is a relatively simple test that demonstrates a flexible epoxy's inability to resist creep-rupture. Information about how you can perform this test yourself can be found in the paper NOTCHED BEAM TEST FOR CREEP-RUPTURE 002-815, published by Gougeon Brothers.
Working Temperatures
Ambient temperature has a profound affect on the working or handling properties of uncured epoxy as well as its rate and degree of cure. A change in temperature will drastically change epoxy resin's viscosity, or thickness. The viscosity of water varies little with temperature changes until it either boils or freezes. However, temperature's affect on the viscosity of epoxy is much more obvious. As the temperature drops, epoxy becomes proportionally thicker, reducing its ability to flow out. This change has three important consequences when working with epoxies in cold conditions.
First, it is more difficult to meter and mix the resin and hardener. The cold resin and hardener do not flow through the dispensing pumps easily and the thicker material clings to the surfaces of the pumps, containers and mixing tools. Colder and thicker resin and hardener take much more time and effort to blend thoroughly. The potential for inaccurate metering and incomplete mixing, compounded by a less efficient chemical reaction, greatly increases the possibility of a deficient bond.
Second, the epoxy is much harder to apply. Cold temperatures make it much more difficult to coat and wet-out surfaces with epoxy. In coating applications at low temperatures, the epoxy mixture will not flow out as easily resulting in thicker, uneven coats that require more sanding to achieve a smooth finish. In bonding applications, the thicker epoxy may not wet out or penetrate porous surfaces enough for a reliable bond.
Third, air bubbles may be introduced during mixing or application and held in suspension due to the chilled epoxy's increased viscosity. Air bubbles reduce epoxy's strength in a bond and a coating's effectiveness as a moisture barrier. In addition, air bubbles show through clear coating applications.
We've told you all of the reasons why using epoxy in cold weather is difficult and risky. However, this doesn't mean that you can never use epoxy in cold weather. With a little advanced planning and by observing the following eight precautions, most of these problems can be overcome and their consequences avoided. We've used these techniques for over 20 years, because they help assure dependable epoxy bonds in cold weather.

-------------------------------------------------------------------------------------------------------------------------

Excellent read Keith, Thanks!

Call me a "wussie" but I'll retreat indoors to use expoxy in near freezing temperatures.

Why endure that which need not be endured?

"Stupid hurts!" - the late John Wayne

SuperDave wrote:Call me a "wussie" but I'll retreat indoors to use expoxy in near freezing temperatures.

Why endure that which need not be endured?

"Stupid hurts!" - the late John Wayne

Absolutely, the warmer the better.

IMO, The only real distinction for epoxy set is working time and being able to "wet out" the piece we are working on quickly, as it pertains to us.

Most of the time we don't mix a large quantity of epoxy for our modeling needs. I usually mix mine on tin foil (sometimes a 3x5 card, but it seems to absorb some of the epoxy). You can spread it out to keep the bulk down and it will remain cooler, increasing the work time.

I have seen folks mix fiberglass resin in containers similar to a sour cream tub and have the entire batch fire off into a solid block. Because the curing process gives off heat and is accelerated by heat, having the resin in a confined area will cause it to heat more, cure faster, heat more, cure faster, etc. to the point that the tub will melt away leaving a chunk of wasted epoxy.

That being said, I will sometimes use a heat gun to warm the epoxy after applying it to a firewall. This thins it and allows it to soak into the plywood more easily. It also smooths the surface out.

Bought some Loctite 5 min epoxy,,and as it states,,you have EXACTLY 5 min once 1/2 mixed to apply before it turns into a block. It fires off real fast.

I bought a bunch of the Great Plains graduated epoxy cups. A very nice product. Allows you to get the amount just right.
http://www.amazon.com/Great-Planes-Epoxy-Mixing-Cups/dp/B001BHEGTW

I often use discarded plastic church communion cups to mix small quantities of epoxy.

For larger quantities I use small discarded aluminum-foil jam containers such as are used in restaurants.

My wife finds it embarassing when I scrounge these at church or from restaurants.

My response: "I'm giving discarded items a "second life, am I not?"

SuperDave wrote:I often use discarded plastic church communion cups to mix small quantities of epoxy.

For larger quantities I use small discarded aluminum-foil jam containers such as are used in restaurants.

My wife finds it embarassing when I scrounge these at church or from restaurants.

My response: "I'm giving discarded items a "second life, am I not?"

I like to use the fast food fish restaurant condiment plastic cups with the lid. Just pick up an extra unused one or two and you are set and ready to mix epoxy.

Jello pudding cups
NyQuil dosing caps
Applesauce cups

Get yourself a box of nitrile gloves. This eliminates the problem of cleaning epoxy from your hands.

lousyflyer wrote:Jello pudding cups
NyQuil dosing caps
Applesauce cups

Get yourself a box of nitrile gloves. This eliminates the problem of cleaning epoxy from your hands.

What removes epoxy from skin? Alcohol perhaps? I hate the feel of gloves when working.

Ron:

As for me I don't have a problem getting epoxy on my hide. CA is an entirely different matter as it is less viscous and flows where it wants to.

When applying epoxy I use a scrap of 1/16" poplar plywood as a spreader and NOT my fingers. Duh?

cribbs74 wrote:

lousyflyer wrote:Jello pudding cups
NyQuil dosing caps
Applesauce cups

Get yourself a box of nitrile gloves. This eliminates the problem of cleaning epoxy from your hands.

What removes epoxy from skin? Alcohol perhaps? I hate the feel of gloves when working.

Alcohol does the trick Ron as do certain brands of 'thinner'.

I'm with you on gloves but they force me to wear them
When I'm performing at my combined Gynaecology
And indoor hang gliding clinic.

"When I'm performing at my combined Gynaecology And indoor hang gliding clinic." - JB

JB:

Strange, I had you pegged as a practictioner of Proctology.

John Goddard wrote:

cribbs74 wrote:

lousyflyer wrote:Jello pudding cups
NyQuil dosing caps
Applesauce cups

Get yourself a box of nitrile gloves. This eliminates the problem of cleaning epoxy from your hands.

What removes epoxy from skin? Alcohol perhaps? I hate the feel of gloves when working.

Alcohol does the trick Ron as do certain brands of 'thinner'.

I'm with you on gloves but they force me to wear them
When I'm performing at my combined Gynaecology
And indoor hang gliding clinic.

Jonny has had a few drops in his coffee this morn I think.

Ron and JB:

Keith will kill me for revealing the story of how he had his hands stuck together with CA by a robber in the grocery store where he worked in high school.

You tell 'em Keith.

Its a scary deal,,lemme say. Once they ran up front to grab the cash,,ell peelo the skin/hands apart from around the support pole. Still have some scarring on my hands from that deal.

Eeeewww

If you use epoxy as I do just about every day as part of my job, you learn to love and hate it. To me, the only thing worse than epoxy on my skin is cat crap on my shoes.
The best way to clean epoxy from skin is plain old soap and water, provided that the mix has not begun to "set". If the mix has started to cure, you now have to use a solvent to dissolve the goo.
If the cure is not too far along, rubbing alcohol works pretty well.

The problem with wiping epoxy off your hands with a solvent is that you are actually wiping it "into" your skin as well as off of it. Once you dilute the mix by wiping it with a solvent, the curing process may stop altogether. Now you have uncured epoxy on your hands and sooner or later you will scratch your nose or rub your eyes, or worse.

I worked with a guy that lived very close to our job, and he would sometimes go home for his lunch break. One day he went home and had a "romantic" lunch with his wife. About an hour later he got an emergency call from home. His wife had developed a terrifying rash in a very private area of her body. Thank you Mr Epoxy!

On a different note, if you get five minute epoxy on your fingers and grab a hot soldering iron, it smells just like Fritos.

Harbor Freight sells nitrile gloves by the box of a hundred for seven dollars.