Just how reliable are Polyurethane Wood Adhesives?

[scrimper]

For the last 30 odd years I have always used PVA for gluing up my timber but recently I bought a tub of this stuff http://www.toolstation.com/search.html?searchstr=93568 I have used it for a few jobs and have found it very useful so far.

Now I glue up lot's of softwood boards by laminating narrow strips and I have always used PVA, clamped them and left them overnight before putting them through the thicknesser but today I wanted some small panels quickly so I glued the strips up the same but using Polyurethane Wood Adhesive (5 min stuff) rather than PVA, after about 15 mins I run them through the thicknesser to my surprise the joints looked very good and try as I might I could not break the panels apart, even the bit's I trimmed off the end broke on the timber rather than the glue line when I snapped them.

Just how dependable is Polyurethane Wood Adhesive, is it a bad idea to use it to laminate boards, I would appreciate some comments on the use of this stuff.

 

[Anonymous]

As a pro I find PU glues fantastic, about a year ago I stopped using pva and switched totally to PU, as far as I can see there are no disadvantages, OK so you have to glue up a bit quicker but thats about it.
Clamping time is reduced dramatically, the joints are stronger, cleaning up is quicker. PU is superb.

 

[Russell]

PU adhesives are fine Fast grab even say there's is seawater proof

 

[scrimper]

Hey thanks for the instant replies.

This type of adhesive is new to me and the daft thing is that I almost felt guilty using it, it seemed to be cheating that it worked so quickly.

From your comments it seems that it's well worth using, the only downside I suppose is it's short shelf life and it's very sticky on the hands!

Any preference between the 5 min or the 30 min type?

 

[bobscarle]

Be careful getting it on your hands, it does not wash off. Either wear gloves or wear the glue for a few days!

Apart from that, I can only echo what the others have said.

Bob

 

[Niki]

I'm using the 30 min type but as I know the clamping time is about 3 hours and total curing 24 hours.

I use Nitro-thinner to clean my hands (every 2~3 min) during gluing, it dries the skin a little bit but any hand cream will cure the problem and it's better than having stained hands...

niki

 

[inventor]

The current issue of Fine Woodworking has an article testing glue strengths.
http://www.taunton.com/finewoodworking/ ... x?id=28897
(subscription only). They made bridle joints with various fits and in various timbers and tested them to destruction with various glues. They say that a joint made with polyurethane glue averages 58% of the breaking strength of a joint made with PVA. Loose joints, where the glue has to fill a gap, were even worse. The polyurethane glue they tested seems to be "Gorilla Glue",
http://www.toolpost.co.uk/pages/Finishe ... ml#Gorilla

Plus, the glue scrimper is using, http://www.toolstation.com/search.html?searchstr=93568
claims "Conforms to EN 204. D4 Strength." Anyone know what this means? Is there a definition of EN204 strength designations out there anywhere?

 

[tnimble]

I don't like PU glues. Is very nasty unhealty stuff. You need to be careful not to spill any drops on the wood and squish out is more easily removed without staining the wood. although it has filling ability its not strong. The more the glue foams the weaker it gets.

The last time I used it on a mitred joint the joints failed while putting in the slot for the reinforcement. And yes the joint was flat, closed and clamped good while drying. The next joints I did with tidebond 3 they didn't fail not even when trying to slightly pull a test piece apart by hand.

 

[Russell]

There is a barrier cream by liberon called glove put that on your hads first before gluing it should wash off then.

 

[Paul.J]

I have been using PU for the first time on my garden bench that i am making,and have to say that i am well pleased with it.Though i have only used it for the M&T joints that i have used.It seems strong to me.
I was worried about all the over flow it makes but this just cleaned off easy with an old chisel .So for any more outdoor projects i will use it again.
I did get it on my hand the once,forgot to put gloves on and it did go black and would not come off,so used a fine sanding stick to get the worse off :roll: Was thinking about some sort of barrier cream for future use.
Paul.J.

 

[mailee]

yep, fingers full of it at the moment! I use a pumice stone to take off the worst and let the rest wear off. As you can tell I forgot to use my gloves with it. Black hairy fingers make me look like a Silverback. :lol:

 

[scrimper]

I don't like PU glues. Is very nasty unhealty stuff. You need to be careful not to spill any drops on the wood and squish out is more easily removed without staining the wood. although it has filling ability its not strong. The more the glue foams the weaker it gets.

Are you saying that it is bad for ones health?

As far as staining goes I found it better in this aspect than PVA, overflow of PVA seems to soak well into the fibres of the timber and makes the wood difficult to take finish, with the PU I just wait till it's dry and remove the surplus with a sharp knife or chisel.

Surely though the PU must be a bit better than PVA on uneven surfaces? PVA has no gap filling properties and is useless if the fit is not good?

I shall continue to use PVA for my main board construction where time is not of the essence if only because PVA works out a lot cheaper especially when one buys in quantity.

As I said I am new to PU so I am not trying to cause any arguments about the stuff but I am trying to promote discussion so that I can learn all the 'ins and outs' of using one adhesive over the other.

 

[Jorden]

I'm starting to have suppositions about PU glue, it does a good job in filling and seems very strong, but i've just had a garden gate fall apart after 18 months of exposure. The wood is still sound, in every joint on the gate the PU glue had failed... Makes me worry about the other jobs I've done using it...

Dennis

 

[scrimper]

I'm starting to have suppositions about PU glue, it does a good job in filling and seems very strong, but i've just had a garden gate fall apart after 18 months of exposure. The wood is still sound, in every joint on the gate the PU glue had failed... Makes me worry about the other jobs I've done using it...

Dennis

So it might not be as good as the makers infer, TBH though I don't use glue anyway for outdoor projects as I would not like to trust it given the wide weather differences we have in England.

 

[Jake]

What brand and type of glue was that Jorden?

I love the stuff, the speed with which it sets is just so convenient. Have moved to Balcotan Rapid on Chris Woodhead's recommendation (thanks!)which is excellent at least from a short term point of view.

Trying to remember the latex gloves is the worst part.

 

[tnimble]

I don't like PU glues. Is very nasty unhealty stuff. You need to be careful not to spill any drops on the wood and squish out is more easily removed without staining the wood. although it has filling ability its not strong. The more the glue foams the weaker it gets.

Are you saying that it is bad for ones health?

Urethane if not acutely toxic but do fall into the group of animal and human carcinogen. The amount of urethane in PU glue is very high compared to what is found in nature that is becomes a hazard.

As far as staining goes I found it better in this aspect than PVA, overflow of PVA seems to soak well into the fibres of the timber and makes the wood difficult to take finish, with the PU I just wait till it's dry and remove the surplus with a sharp knife or chisel.

Remove pva after about a little drying (about 20 minutes or so) time with a putty knife of wide chisel. It comes off without any stain to the wood.

with PU you must wait for has complete set any pressure on the glue while not complete set generates huge staining problems. When removed after a complete cure with a sharp chisel of scraper the top layer of fibers is stained and has to be sanded down. The area involed in squise out is also much largers than with pva du the the runnyness and foaming of the glue.

Surely though the PU must be a bit better than PVA on uneven surfaces? PVA has no gap filling properties and is useless if the fit is not good?

It does fill gaps but give not much strength when foamed up. When something has to be glued that has a gap either glue a few peices of paer with pva or use epoxy glue.

 

[Jorden]

Hi Jake

It was Gorilla glue, I don't use a great deal of it so only buy small quantities. The glue was fresh from the supplier (Axminster) and applied according to manufacturers recommendation. I re fixed the gate using Titebond 3 and it seems to be holding up.

Dennis

 

[Anonymous]

Srimper

One of the US mags (Fine woodworking i think) just carried a review of differnet adhesives. Nice and detailed with testing to failure in a lab

 

[David C]

PU is bad for your health if not used carefully.

Try not to inhale fumes, i.e. good ventilation.

It may cause serious allergy after repeated skin contact just like Epoxy, so disposable gloves a good idea. I do not know whether a barrier cream is sufficient?

I very much like the Bison Glue in cartridges from Tilgear, originally recommended to me by Bruce Luckhurst. Very long shelf life after opening, due to lack of damp air in the 'container'.

David Charlesworth

 

[Joe90]

.... It may cause serious allergy after repeated skin contact just like Epoxy, so disposable gloves a good idea. ....

Is this correct? (I.e can an allergy develop after repeated use where a single use doesn't show problems?)

I use epoxy two part putty from time to time and I mix it in my fingers.... the box does say that some people with sensitive skin may have an allergy... since I don't seem to have a problem i don't use gloves as it sticks to them and is hard to mix. I wash my hands immediately after use. The box doesn't say that an allergy can develop over repeated exposure (but then why would it, presumably a full Safety Datasheet may mention this?).

I think I'll now have to mix using a putty knife which will be more difficult.

In regard to spraying AC lacquers it appears that a sensitivity can develop over time to the extent that even small exposure can cause feelings of nausea when originally it didn't... Info from Morrellls which seems very authorative. So wearing a respirator would seem to be absolutely mandatory... most people would agree with this would they?

Cheers
Joe