Moisture and epoxy

[paul.norton]

Without contacting specific manufacturers, what is the accepted maximum moisture content of timber when gluing with epoxy resin.

Paul

 

[electrosys]

Dunno about epoxy, but I've just bought some new-fangled D4-grade resin-based adhesive, which specifies <15%.
Which is a bit academic, as I have no means of measuring moisture to that accuracy.

 

[oldsaltoz]

Without contacting specific manufacturers, what is the accepted maximum moisture content of timber when gluing with epoxy resin.

Paul

Basically as dry as you can possible get it, most epoxy resins do not well at all with any moisture present, keep in mind that rot will continue even sealed in epoxy.

Another trap is the oil content of some timbers, Teak is a good example.

Adding Micro-fibres to the mixed epoxy will make a very strong joint, when testing to destruction I found the timber Several types tested) broke before the epoxy joint.

Good luck and fair winds.

 

[Deleted member 36384]

Moisture Content of Wood For Epoxy Glue

Epoxy adhesives cure by a different chemical process. They neither contain water, nor is water necessary for them to form bonds with wood. Epoxies can therefore perform very satisfactorily below 6% m.c. as well as giving excellent bonds up to 20% - 25% m.c., well outside the limits of the other glues. Kiln dried timber often has a moisture content well below 8% and is therefore best glued using epoxy adhesives.

Source
http://www.azom.com/article.aspx?ArticleID=1093#_Wood_Moisture_Level

For wood to rot, it needs three things: a particular moisture content, a range of temperature, and oxygen. Over the range of temperature we have no control. However, we can use epoxy coating to keep the moisture and oxygen out. We use only kiln dried wood in our boats. Kiln drying will bring wood down to a 6% to 8% moisture content. Wood only rots at about 20% moisture content. That's a lot of water that would have to enter the wood to bring it up to that moisture content. With our epoxy coating and careful construction techniques, we can keep the moisture content very close to the content it had when we epoxied it. Even if there were to be some breach in the coating, that would only be a local breach. Damage to the boat would be confined to the immediate area, allowing time for repair without any real damage occurring. Rot will not be a problem if you get the damage repaired within a reasonable time. That said, we have never had a case of rot in any epoxy coated boat we have built. None. Part of the credit for this must go to our clients, who love their boats and take good care of them.

Source: Note that the source below is describing West System Epoxy
http://www.nexusmarine.com/about_epoxy.html

 

[Poignard]

Without contacting specific manufacturers, what is the accepted maximum moisture content of timber when gluing with epoxy resin.

Paul

A rule-of-thumb I use is to sand-paper the timber. If that produces dust then it's dry enough to epoxy.