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View PPK's profile

What type of Epoxy?

by PPK
posted 10-17-2018 04:44 PM


24 replies so far

View RobHannon's profile

RobHannon

321 posts in 1074 days


#1 posted 10-17-2018 04:54 PM

Never used the stuff from HF, but had no issues with Devcon, Locktite, Hobby King, etc. for adhering.

I agree West and System 3 are probably not the most economical solution for small surfaces.

View Aj2's profile

Aj2

2535 posts in 2342 days


#2 posted 10-17-2018 04:58 PM

I use West systems with the 206 slow hardener. It has it place but it also has some drawbacks. In some woods it will leave a dark glue line, it’s very expensive so mixing up the right amount without being wasteful is challenging.
Mostly I use tite bond or plain old Elmer’s glue. I try to carefully plan my glue up in the cool mornings evenings.

-- Aj

View DrDirt's profile

DrDirt

4592 posts in 4286 days


#3 posted 10-17-2018 05:06 PM

West Systems, and System 3 are the same company now.

For Joinery stuff – I use “T-88” from System 3.
Available a lot of places, I get it on Amazon.

Gel time is 60 minutes, full cure is 72 hours, but generally I find it is an “overnight” clamp-up and is no longer tacky… just takes 72 hours to be at full strength.

Comes in many sizes from 1/2 pints to gallons.
https://www.systemthree.com/products/t-88-structural-epoxy-adhesive

-- “The two most important days in your life are the day you are born and the day you find out why.” Mark Twain

View John Smith's profile

John Smith

2052 posts in 706 days


#4 posted 10-17-2018 05:52 PM

there are dozens of good epoxy products on the market.
you just have to weed through them to fine one that works for you.
I keep a supply of the West System G/flex 650 on hand. it is a slow set
and easy to work with – and cheaper than the quart kits.

.

-- I am a painter. That's what I do. I paint things --

View Redoak49's profile

Redoak49

4241 posts in 2532 days


#5 posted 10-17-2018 06:00 PM

I use a couple brands. I recently have been using System 3 T88 for a Maloof style rocker and it works fine.

I also use Bob Smith from Amazon in both Quick Cure and Mid Cure with very good results. I mix it by weight using a small digital scale.

View CaptainKlutz's profile

CaptainKlutz

1959 posts in 2038 days


#6 posted 10-17-2018 06:18 PM

All clear retail (IE sold in retail store) epoxies are basically same stuff. :(

Best example – Bob Smith Industries provides private labeling programs for any hobby shop or distributor that buys in bulk. That is why Hobby Lobby/Rockler/Woodcraft epoxy or cyanoacrylate adhesives all come in same bottle(s) and look almost same – they are same!

The key difference between the hardware store 5/10/15/60 minute cure varieties sold in less than 1 quart bottles is the type of curative used. They all use similar blends of same resins (bisphenol A diglycidyl ether & bisphenol F diglycidyl ether, with maybe some low viscosity reactive diluent oligomers).

The FAST cure (less than 15 min) types use an aromatic amine curative that reacts quickly and is least temperature sensitive of typically retail epoxy curatives. These are most forgiving of stupid human tricks, like mix ratio errors, or cooler temps. :)

The SLOW cure (30 minute plus) types use an polyimide curative that reacts much slower, and cure speed is much more dependent on ambient temp. Some will NOT cure at all below 60F, or will take weeks to cure, and months to reach full strength. These are less forgiving of stupid human tricks; such as mix ratio errors, and dirty bond surfaces, etc.

Generally speaking, The shorter the cure time; the lower bond strength, and lower bond strength is at elevated temperatures. So despite challenges with longer cure time epoxies, one should always use the longest cure time your process allows for best adhesive performance. Also must know that while fast/slow epoxy may begin cross linking and ‘set’ in 5 or 30 minutes, that full bond strength is not reached for days, some even require weeks (length of time is temperature dependent).

The small bottle retail epoxies described above are different than epoxy systems typically sold by West Systems, System 3, etc; in quarts and gallons. These epoxies were developed for (fiberglass, Kevlar, carbon fiber) composite lamination of water and air craft parts. These laminating resins have significantly lower viscosity to help with fabric wet out. They use slightly different resin and curative blends to provide this lower viscosity. These lower viscosity resins typically have lower bond strength (PSI), but when used over large area strength is not as important as flexibility or consistent performance across a wide range of temperatures.

The strength of laminating resin .vs a structural resin is mute point for most wood working applications. We really only need to be concerned with shear strength and peel strength. Practically every retail branded structural or laminating epoxy is stronger than wood in these stress modes. :)

So you can choose an epoxy to use for wood working based on how much time you need for assembly, clamp retention time, ambient temperature during assembly & cure, and even price. :)

Hope this helps explain hobby epoxy for you.

PS –
There are also retail structural epoxies intended for metal bonding, these are typically grey or black in color. This ‘metal’ epoxies use powdered metal as fillers, and weak acids that react with epoxy system to etch the metal for stronger bond. JB Weld is common brand, and it uses flake aluminum powder to help dissipate heat in epoxy and improve high temperature performance. Devcon/Loctite sell a black epoxy that uses powdered steel as filler for bonding metal castings. These can be used for bonding wood, but would not be best choice.

NOTE:
The above is extreme simplification of differences between varies retail epoxy types. There many more subtle differences left out, and many more epoxy systems available from commercial/online sources that some might consider retail materials. If you need more information on epoxy adhesives, PM me offline, and I can suggest a couple of polymer reference books for your library. :)

Best Luck!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View PPK's profile

PPK

1548 posts in 1353 days


#7 posted 10-17-2018 07:14 PM

Capt. Klutz! Wow, thanks! Very interesting. I learned a lot.

The strength of laminating resin .vs a structural resin is mute point for most wood working applications. We really only need to be concerned with shear strength and peel strength. Practically every retail branded structural or laminating epoxy is stronger than wood in these stress modes. :)

So you can choose an epoxy to use for wood working based on how much time you need for assembly, clamp retention time, ambient temperature during assembly & cure, and even price. :)

- CaptainKlutz

This does not surprise me, makes sense. ^

-- Pete

View PPK's profile

PPK

1548 posts in 1353 days


#8 posted 10-17-2018 07:16 PM

John, Dr. Dirt, Red Oak,
Looks like the T88 or Gflex 650 would be great options for me – not huge amounts and reasonable price. Thanks for the help!

-- Pete

View ArtMann's profile

ArtMann

1442 posts in 1360 days


#9 posted 10-17-2018 08:56 PM

Is it a “mute” point or is it a “moot” point?

View newwoodbutcher's profile

newwoodbutcher

794 posts in 3394 days


#10 posted 10-17-2018 09:52 PM

Thank you Capt. Klutz! For your time, effort and helpfulness. Very well written and informative

-- Ken

View OnhillWW's profile

OnhillWW

196 posts in 1776 days


#11 posted 10-17-2018 11:12 PM

C Klutz nice post, most appreciated. I have used a lot of epoxy and this fills in a lot of gaps in my understanding.

-- Cheap is expensive! - my Dad

View MJCD's profile

MJCD

598 posts in 2915 days


#12 posted 10-17-2018 11:18 PM

I’ve used the West System G/flex 650 extensively; and, aside from the epoxy-associated issues, it is excellent.

Epoxies tend to leave a thicker, more noticeable glue-line (though TB3 is noticeable on light woods); and is much more expensive. The longer open time is very helpful in specific situations; and, in exterior work (outdoor benches, for example), I would default to epoxy.

These days, all interior builds are TB3 (Titebond III).

MCJD

View CaptainKlutz's profile

CaptainKlutz

1959 posts in 2038 days


#13 posted 10-18-2018 01:13 AM

Couple more data points for those that care about epoxy differences:

1- The epoxy systems designed for composites mentioned above can have significant differences in material properties depending on curative used, even with same resin. While most people only look at whether curative is fast, med, or slow; these same curatives can provide significantly different values for hardness, flexibility, water resistance, or clarity (yellowing). So while picking your curative for optimum cure time, be sure to check the overall properties are what you need.

2- There are many epoxy suppliers available online. Not saying anything bad about West Systems, or System 3 ‘retail’ brands; but if your application needs quarts/gallons of epoxy, WWW has cheaper sources. I have used Fibreglast for many, many years with great success. Us Composites private label epoxies also offer nice price break with as few as 2 gallons. :)

3- If you are interested in longevity of epoxy in any surface coating applications where you want minimal yellowing as it ages, do not forget to protect the epoxy with UV inhibiting top coat. ALL epoxies will turn yellow as they age and are exposed to UV, even the ‘clear’ top coat epoxies sold for coating bar tops.

Best Luck!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View lumbering_on's profile

lumbering_on

578 posts in 1034 days


#14 posted 10-18-2018 01:32 AM



Is it a “mute” point or is it a “moot” point?

- ArtMann

Technically, it should be a ‘mute’ point, as ‘moot’ means something that is arguable. This is why law students participate in a ‘moot court’. However, as with so many misspoken phrases, the term ‘moot point’ is considered something not worth arguing.

It’s like when you hear someone say ‘pompom’ when the term is actually ‘pompon’. A ‘pom-pom’ is actually a British naval gun.

View Pixxture's profile

Pixxture

27 posts in 615 days


#15 posted 10-18-2018 01:41 AM

I have seen marine epoxies at the big box stores. Does this mean some epoxies are affected by moisture or water?
I had always thought epoxies were waterproof.

View Kelly's profile

Kelly

2472 posts in 3488 days


#16 posted 10-18-2018 05:19 AM

I’m with the Capin.

I started buying larger quantities because of the infinite uses to which I can put it.

The last go round was two to one mix and I enjoy the long open time, and the fact it flows enough I can even use it to harden wood. Waiting twenty-four hours is just to be expected to me, since, if you’re going be using epoxy, you probably already expected to have to wait a while.

I think you’d be hard pressed to be able to show it was significantly weaker than 3-M or other brands.

View CaptainKlutz's profile

CaptainKlutz

1959 posts in 2038 days


#17 posted 10-18-2018 05:10 PM



I have seen marine epoxies at the big box stores. Does this mean some epoxies are affected by moisture or water?
I had always thought epoxies were waterproof.
- Pixxture

Water Proof or Moisture resistant? Epoxy? Adhesive or Coating? Which chemistry is being used?

Short answer:
Yes, ‘epoxy’ can be affected by moisture!

Long answer:
Depends…..

First: Key part of the ‘water proof’ performance of any polymer depends on conditions for: temperature, pressure, and PH. Using epoxy at room temp with atmospheric pressure can make it look waterproof. But same epoxy subjected to high pressure steam, or an acidic liquid, and it will fail in minutes/hours

While epoxy is considered to be more resistant to water permeation/absorption than other polymer materials, epoxies are not 100% ‘waterproof’. Some are just more resistant to water than others. :) Aliphatic epoxy systems are generally more water resistant than aromatic epoxy systems, and usual what is sold as ‘marine epoxy’.

Hmm, Could spend pages explaining this topic.

Good example reference: Sherwin Williams offers every practical epoxy chemistry used in epoxy coating market. This PDF comparison of chemistry types shows differences in final properties.
These same curative chemistries are used by epoxy adhesives (although maybe not available at retail), but I am unable to find an online comparison documentation ATM.

BTW –
If you really, really, really want to see the kind of engineering work that goes into finding the perfect epoxy for use with wood, try reading this NC State University paper on epoxy selection for engineered wood (glue lam beams).
My favorite part of paper is 1st conclusion:
None of the epoxy variations tested had any impact on overall strength performance.
Hahahaha – Just as I posted earlier, most all epoxies will work for wood bonding. :)

My apologies for diving into a rabbit hole on this topic; I have spent over half of my 35 year professional career, developing materials, and processes involving epoxy, polyurethane, & silicone polymer systems for electronics industries. Bonding wood is easy by comparison…....

Cheers!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View Pixxture's profile

Pixxture

27 posts in 615 days


#18 posted 10-18-2018 09:38 PM

Captain
THANX!
Thats quite a bit of info. I will never understand the chemistry, so thanks for the words of explanation. :)

View ArtMann's profile

ArtMann

1442 posts in 1360 days


#19 posted 08-06-2019 02:20 AM

Is games77 a spammer?

View Kelly's profile

Kelly

2472 posts in 3488 days


#20 posted 08-06-2019 02:39 AM

Yep. You nailed it. Dirt bags abound.


Is games77 a spammer?

- ArtMann


View shipwright's profile

shipwright

8401 posts in 3342 days


#21 posted 08-06-2019 05:58 AM


The small bottle retail epoxies described above are different than epoxy systems typically sold by West Systems, System 3, etc; in quarts and gallons. These epoxies were developed for (fiberglass, Kevlar, carbon fiber) composite lamination of water and air craft parts. These laminating resins have significantly lower viscosity to help with fabric wet out. They use slightly different resin and curative blends to provide this lower viscosity. These lower viscosity resins typically have lower bond strength (PSI), but when used over large area strength is not as important as flexibility or consistent performance across a wide range of temperatures.

- CaptainKlutz

Lots of good information here but I have to disagree with the characterization of WEST and System Three epoxies as low viscosity laminating resins. I was never a WEST fan and won’t speak for them although I’m pretty sure my point applies to them as well.
When I was building boats I used many many gallons of “marine epoxy” from a company called Industrial Formulators of Canada which has since been bought out by System Three. IFC offered a wide range of epoxies for all kinds of purposes, some with special bonding additives for oily woods, some food grade, some for cloth lamination, etc, etc.
Some were very high viscosity and some were very low.
Most of these products are still sold by System Three, many under the same names (ColdCure, S1 sealer, etc.)
My advice to anyone who is looking at using epoxy for a specific purpose is to talk to an epoxy supplier who knows his product and take their advice.
I was lucky enough to have known Jim Peters who was the chemist who founded IFC and was able to get my advice directly from him. There is a lot of complexity in the subject of epoxies.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View CaptainKlutz's profile

CaptainKlutz

1959 posts in 2038 days


#22 posted 08-06-2019 07:05 AM


..
My advice to anyone who is looking at using epoxy for a specific purpose is to talk to an epoxy supplier who knows his product and take their advice.
..
There is a lot of complexity in the subject of epoxies.
- shipwright

Ahmen!
Have worked with every major raw material supplier and formulator in world on epoxy resins, curatives, and modifiers; for several decades in automotive, aerospace, and electronics products. Even if you are a part time formulator like me with a half dozen adhesive patents and own a cabinet full of raw materials to make your own formulas, it it best to work with your local supplier for a solution. :-)

It IS extremely hard to generalize any mfg. All I was comparing was classic small bottle 5-15-40 minute cure retail grades to the common named epoxies sold for boat or aerospace lamination sold in retail stores. It was not meant as all encompassing. Most mfg make structural and laminating systems, plus hundreds of specialty systems designed for special bonding cases. Picking right one can be very hard.

There are volumes of books on the topic and college degrees available if you want to learn more.

#IAMAKLUTZ, not any sort of an expert.

Cheers!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View shipwright's profile

shipwright

8401 posts in 3342 days


#23 posted 08-06-2019 02:41 PM

CaptainKlutz, you would have enjoyed talking to Jim.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View WoodenDreams's profile

WoodenDreams

806 posts in 455 days


#24 posted 08-06-2019 08:16 PM

Good information….......

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