wood adhesives for glulam components
wood adhesives for glulam components
(OP)
We are building some glulam components for a personal building. I am finding it difficult to source a product in the USA. We are primarily targeting a single part adhesive that will air dry without heating. I am open to 2 part adhesives but the air dry will be a stiff requirement.
We will be gluing CDX plywoods to dimensional SYP with a target shear strength to meet or exceed 1000psi. That seems to be about all plywood can hope to handle so I don't see a need to target glues outside the ability of the substrate.
One product we have stumbled across is MDI. I have yet to find a good source of information to select the right glue. Right now I would like to use a type I glue but I have not see how prices look on these products and this is a cost sensitive project. We intend to obtain samples and do in-house testing to ensure our procedures are good.
We will be gluing CDX plywoods to dimensional SYP with a target shear strength to meet or exceed 1000psi. That seems to be about all plywood can hope to handle so I don't see a need to target glues outside the ability of the substrate.
One product we have stumbled across is MDI. I have yet to find a good source of information to select the right glue. Right now I would like to use a type I glue but I have not see how prices look on these products and this is a cost sensitive project. We intend to obtain samples and do in-house testing to ensure our procedures are good.






RE: wood adhesives for glulam components
Have you checked the bond stress for your design case? Normally the home handyman does not have the equipment to make a proper I section, so you either end up with two layers of plywood sandwiched over the flanges or four wood flanges with plywood in the middle. If that were the case I would not expect the bond stress to be as critical. Also, your contact area tends to be many magnitudes greater than what manufacturers offer. West makes some very good epoxies and the benefit with those is you do not need the clamping force that many other adhesives require. I like their West 610 system, but the cost is very high per unit volume. The glulam manufacturers use a resorcinol adhesive (casein years ago), and that requires in excess of 100psi to generate the bond stress it is rated for. I have heard stories of some that have used it in similar cases without the clamping force the glulam guys generate, but I never have. Another option may be a polyurethane like PL Premium. It is rated as a structural adhesive. I made some flooring inlays (5mm Tigerwood over baltic birch plywood made in a vacuum press) a few years ago and I tested several different adhesives by soaking them. This test is not all that appropriate for your case, but the PVA bonds failed, so did the Unibond, but neither the epoxy nor the PL Premium failed after the finish wood was fully saturated.
Be careful about the moisture content of your flange sections. If you are buying from a typical supplier this could be a challenge.
Good luck.
RE: wood adhesives for glulam components
Who might I contact for adhesives?
RE: wood adhesives for glulam components
I would do some tests with a polyurethane or epoxy. The clamping force generated by screws or nails is quite variable, so I would aim for an adhesive that requires the minimum clamp force. Comparing to what others might do is tricky unless you know the equipment they have.
Measure the moisture content of your lumber. I still don't quite follow what you are building, but glulam production requires strict controls on wood moisture contents. The moisture content of each piece must comply with certain limits and the difference between various pieces is also measured. Large shrinkage stresses will destroy many glue bonds.
RE: wood adhesives for glulam components
I did a popsicle stick bridge project with my daughter when she was in high school. We sanded the sticks before gluing to improve bond. Her bridge ended up breaking the test weight apparatus used to judge the contest!
RE: wood adhesives for glulam components
RE: wood adhesives for glulam components