Epoxy not adhering

[Bodgy]

Just finishing off the back board for an Oregan hall table. There were several tear outs from the plane. These I filled with Techniglue (the slow drying mix). 24 hrs later I planed the board (with a sharp blade) and the glue just lifted off, leaving the self same tear out holes as before.

What am I doing wrong?

[AlexS]

Did you clean the area you're filling with metho first? Also, proportions for epoxy have to be pretty well as specified - near enough is not good enough with it.

[bitingmidge]

Bodgy,

In my somewhat limited experience, ATL's products are very good, and it would be unusual for this to be a fault of the glue.

Possible causes are:

1) Incorrect ratio of the two parts. As Alex said, epoxy needs to be mixed EXACTLY correctly, not guessed. For measuring small quantities I use syringes and measure to an accuracy of about one cc.

2) Incorrect mixing. The two parts must be thoroughly mixed, near enough isn't good enough I'm afraid!

3) Oil or wax contaminating the surface.

4)Dust, dirt or sawdust contaminating the surface (the glue will adhere to the dust ok)

If you don't have one, download a product data sheet http://www.atlcomposites.com/pdf/tech_glue_R60.pdf . If that doesn't solve the problem, contact ATL composites, but don't forget to report back here!

cheers,

P

:D

[knucklehead]

I use the slow set Techniglue a lot.

A couple of questions
1. When the epoxy set was it hard? It should be really hard. If it is not is may not have set properly.
2. Was the epoxy forced in to the voids?

A couple of things to try:
Watch the mixture ratios, mix very well.
Lay it in to the holes with a spatular or the like.
Try and leave the minimum of excess epoxy on the timber. Scrap of the excess with a cabinet scraper.

[JB]

The only two times epoxy resin has failed for me was when it was old and had been overexposed to air, and after a cold night. The cold night failure set hard during the next day.

I haven't used Techniglue brand, but for the record...I use exclusively epoxy resin slow drying glue, and I use a fair bit of it. I guess the amounts, and I suspect I put up to 10% more of one part or the other in each batch. I mix quickly and probably not too thoroughly taking about 5 seconds to mix small amounts (less than a teaspoon) and 10 seconds for larger amounts. Apart from the two failures mentioned above, I have had no failures in hundreds of mixes.

[BrianR]

If the wood has been polished with a silicone based polish sometime in it's life, then that could cause your problem. Silicone is difficult to remove.

[Bodgy]

Thanks guys, I'm afraid I'm probably guilty on all counts.

1. I mix by estimation, ie two lumps of the glue at 2:1 on a ceramic tile. I then mixed thoroughly and then added a pinch of black oxide for colour. I wasn't aware that exact proportions were mandatory.
2. I did thoroughly brush off the work before applying glue. In future I'll blow out the holes etc and then wash off. Alex, I usually use turps, why metho?
3. Whilst it had cured for 24hrs, the glue was not rock hard, still a little softish.
4. After the disaster with the plane I reverted to a scraper and, whilst more tedious, did a far better job at removing excess.
5. I forced the glue into the holes with a spatula. Lots of excess, which was a pain to clean up. Learnt this lesson!
6. First failure, all previous use in gluing joints spectacularly successful.

Finally, not having used epoxy as a surface filler, I notice the epoxy when fine sanded remains dull. When I finish with shellac and wax I'm hoping these spots will carry the same lustre?

Will try again this PM. Incidentally, the glue adhered well in the nail holes, knot holes etc. Just the plane tearout area's failed.

[AlexS]

Re 1. above; try doing 3 equal sized lumps of glue. I reckon it's easier to be accurate that way than to estimate one lump twice the size of the other. The black oxide shouldn't have been a problem.

Re 2. No special reason, other than I've always used metho. Also, turps sometimes leaves a bit of a greasy feel that can be removed by metho.

[Rocker]

Bitingmidge,

Do you know of a Techniglue retailer who stocks the fast hardener? I ordered some recently from Carbatec, but they were clearly unaware that fast and slow hardeners existed, which is not surprising, since they had stuck a price tag on top of the sticker specifying whether the hardener was fast or slow. The upshot was that I received the slow hardener, which, when I tested it this morning, gave about 55 minutes of working time at 22°C. I am not going to kick up a stink with Carbatec, but it would be nice to find a supplier who took a little interest in the product they are selling, and who supplies what has been ordered.

Rocker

[Bodgy]

Bitingmidge,

Do you know of a Techniglue retailer who stocks the fast hardener? I ordered some recently from Carbatec, but they were clearly unaware that fast and slow hardeners existed, which is not surprising, since they had stuck a price tag on top of the sticker specifying whether the hardener was fast or slow. The upshot was that I received the slow hardener, which, when I tested it this morning, gave about 55 minutes of working time at 22°C. I am not going to kick up a stink with Carbatec, but it would be nice to find a supplier who took a little interest in the product they are selling, and who supplies what has been ordered.

Rocker

Get mine from a place in Perth, good quick service and they will talk to you for advice.

They have a Web site too. Contact: Alf Smallwood, June Rogers, Veronica, ph: 08 9386 8892 fax: 08 9386 8874 Mobile: 0419 965 354 email: [email protected]

[Rocker]

Bodgy,

Thanks; but, seeing that Techniglue is manufactured on the Gold Coast, I was hoping to find a QLD retailer. I have bought it from Timbecon in the past, but I think someone said they no longer ship it interstate.

Rocker

[bitingmidge]

Do you know of a Techniglue retailer who stocks the fast hardener?
I use another brand and buy direct from the manufacturer, but ATL composites nearest distributor to you is:

1. Access Wholesalers 9 Neumann Road Capalaba Qld 4157 PO Box 142 Capalaba Qld 4157

Contact: David Tierney ph: 07 3245 2980 fax: 07 3245 2982 email: [email protected] (Mon – Fri 8.30am -5pm)

Other States are listed here:-
http://www.atlcomposites.com/distributors/index.htm
Cheers,

P

[Bodgy]

Your wish is my ................. (Bloody Cane Toads!)


. Access Wholesalers 9 Neumann Road Capalaba Qld 4157 PO Box 142 Capalaba Qld 4157
Contact: David Tierney ph: 07 3245 2980 fax: 07 3245 2982 email: [email protected] (Mon – Fri 8.30am -5pm)

2. Cast Metal Services 275 Toombul Road Northgate QLD 4013 PO Box 7 Grange QLD, 4051

Contact: Tania ph: 07 3266 6266 fax: 07 3266 6366

(Technirez Tooling only)

3. Huntsman Composites 62 Ingham Road Townsville QLD 4810 PO Box 5824 MC Townsville QLD 4810

Contact: Peter Wark, Dawn Wark, Rod Sawyer ph: 07 4772 3766 Mobile: 015 637 515 or fax: 07 4721 2576 Mobile: 014 669 624 (John) email: [email protected]

4. Rite Price Distributors 3 Energy Crescent Ernest Junction QLD 4214 PO Box 2014 Nerang MDC 4211

Contact: Bob Kolderic, Ray Howlett & Jason Riley ph: 07 5574 5811 fax: 07 5574 5822

(Rapid Cure & Techniglue only)

[Rocker]

Peter and Bodgy,

Many thanks.

Rocker

[RETIRED]

Was the surface rough enough for it to key to? I have found with some tearout that it is "smooth" inside and you have roughen it a little bit.

[Bodgy]

Was the surface rough enough for it to key to? I have found with some tearout that it is "smooth" inside and you have roughen it a little bit.

Spot on , that now totals 4 cock-ups in a single procedure. Some kind of record?

The tearouts (this is Oregan) were quite smooth at the base. As the glue (even with my flawed technique) held in the nail holes etc., I obviously need to roughen up the tearout bases for a better key.

Learnt a lot here, thank you Gentlemen.

[brit_in_oz]

Hi

I work as a development chemist for one of the largest adhesive and selant manufacturers in the world. The problem described is virtually garaunteed to be to do with the suface and not the product.

Epoxies (be they floor sealants or glues) work by a reaction between the resin (virtually always bisphenol A or a derivative), and a hardener / catalyst. If you dont mix enough hardener in then the reaction is slowed down (also caused by lower temperatures). It will, however, ultimately harden, but it can take a lot longer. The reverse is true as well, too much hardener will make the reacton speed up. By changing the catalyst or resin or the ratio's of the two in the tube then other types of epoxy can be made such as 'quick set' types

This site has a good explanation if you interested in thh chemistry
http://www.chem.rochester.edu/~chem424/epoxy.htm

Poor adhesion to a substrate is one of the most common questions we get asked / complained aout. The majority of the time it is down to poor surface preparation. Someof the commmon problems

1. Dirty surface - eg a layer of dust or sirt is inthe hole. The adhesive sticks the the dust and then is easily displaced

2. Surface contaminent, eg a chemical coating. Epoxies dont stick too well to a lot of polymers, they will peel off as in your case This could be a varnish or a penetrating sealant. These form 'low energy' surfaces, (the concept is similar to non stick frying pans) and prevents a bond been formed. the other thing that can happen is that the surface is not wetted out, so the product cures without actually reaching the wood surface .

3. On a clean timber, free from large amounts of resins (eg some oily timbers) most adhesives will bond perfectly. This includes polyurethanes, PVA, solvent based construction adhesives, water based acrylics. In the testing we perform when properly prepared in hearly all cases we find 'fibre tear' , ie the wood surfaces fails or is ripped out, not the glue that fails.

Hope that helps a bit .

[DPB]

Brit, it seems you are qualfied to comment on adhesives.

As I read the previous responses in this thread, based on experience I found myself doubting the frequently stated "rule" that mixture proportions were critical i.e. "Incorrect ratio of the two parts. As Alex said, epoxy needs to be mixed EXACTLY correctly, not guessed. For measuring small quantities I use syringes and measure to an accuracy of about one cc."

I have to confess I have always just eye-balled my proportions and its always worked.

Your comments on this seem to confirm my doubts about the validity of a number of the responses. Have I got this right?:confused:

[brit_in_oz]

Yes your correct, approx will normally do, however, dependingon the type of glue approx in some cases will be better than others, for example a fast curingproduct will be a lot more susceptable to errors than a slow curing one. The worse that willhappen is that it goes off too fast, or that it stays tacky for a long time.Same goes for builders bog type filler, too little hardener and it will take ages to cure, too much and it will go off too quickly

[bitingmidge]

Brit,

You may indeed be chemically correct, but your "near enough is good enough" scares me!! :eek: .

I've seen too many serious problems from incorrect mixing to sit back idly! (It's not a pretty sight watching guys chip "rubber" off a biaxial glass layup on a 40' boat, because they got the mix a "bit" wrong!

It may indeed go off given enough weeks or months, but will it perform to the desired capacity? I have had chemists say no!

I am not qualified to comment on the chemistry, but agree that to my knowledge most epoxies use the same A resin base, however depending on purpose, all have different admixtures and diluents, and different catalysts.

Surely you are making a bit of an over generalisation?

(Don, my DEADLY 1cc accuracy is for small quantities say 15ml max NOT litres at a time, where accuracy is a lot easier to achieve )

I haven't found a manufacturer who will guarantee a product not mixed in correct ratios, or properly and thoroughly mixed, and in my very short "hands-on" time in the industry, the ONLY problems I encountered were as a result of either of the above, chemically correct or not!

I am not having a go at you, I would like to hear your response about the actual rate of cures, what happens to the unbonded bits if the mix is not correct, what is the impact on strength of the bond? I'm thinking if one needed a certain amount of glue, got the mix 10% wrong, then 10% of it wouldn't catalyze, leaving a substantial reduction in bond strength?

Or have the marine and aviation industries just got it wrong? (serious, not sarcastic question!)

cheers,

P


P :D :D

[brit_in_oz]

No offense taken,

I did not mean to imply you should be lazy with volumes, of course following the manufacturers instructions will always given the best results. The only thing I was trying to point out is that for a standard epoxy you do have some play with volumes, though i cannot say what those levels are.

Epoxy curing is a catalysis reaction, its not consumed in the reaction, therefore, the concentration determines the speed of reaction (in addition to the temperature). The problem can occur when different ratio's are used because the mobility of the catalyst is reduced as the reaction continues and the polymer formed,and so it is harder to get access to the next monomer to react with. This is pretty much why the ratios are carefully calculated in a epoxy glue to get the optimum collision rate.
If this was a catalysis reaction in a moving fluid, then it would all be as i stated, that a difference in the ratio would not affect the final outcome just take longer to occur.
I am happy to agree that in a thickened system this may not occur and you may get worse results, however, their is a window in which this will make little difference (though i cannot say what this is depending on product). The worse situation is too little catalyst not too little forthe above reason.

[bitingmidge]

I am happy to agree that in a thickened system this may not occur and you may get worse results, however, their is a window in which this will make little difference (though i cannot say what this is depending on product). The worse situation is too little catalyst not too little forthe above reason.

Thanks, that's what I hope I was getting at. I think while you are technically correct, unless we are chemists, practically we should strictly comply with the manufacturer's instructions!

Cheers,

P (and thanks for not taking offence!)
:D

[stevebaby]

Did you clean the area you're filling with metho first? Also, proportions for epoxy have to be pretty well as specified - near enough is not good enough with it.
I use acetone to clean epoxy joins,particularly with resinous stuff like oregon or pine,or waxy stuff like spotted gum.If you have access to a TAFE library maybe they could get a copy of the Gougeoun brothers book on boatbuilding which has lots of info on epoxies.